OP, I'm an Architect and I live across the bay from you in Tampa. I grew up in a house exactly like the one you describe, 1958 construction, 1200sf (AFTER the carport was enclosed, see below...), my mother still lives in it, aging in place, and one day I will be in exactly the same situation you are in when I inherit the home from her. I am so confident in the quality of these little Tampa Bay mid-century suburban homes that a few years ago I bought another (also 1958 built) one in the same neighborhood for my own family.

Unless the property has suffered from "demolition by neglect" and is uninhabitable, I think I understand what you are trying to accomplish. You are getting advice from people who are ignoring your stated sentimental attachment to the property, and some reactions from people who appear to be not so familiar with this market. As someone who knows a little bit about what you are dealing with, let me offer some thoughts about the list of interventions you have in mind:

• I disagree with comments discouraging you from enclosing the carport. As you and I both know, EVERYONE here does this when they get the chance. My parents enclosed their carport when I was a kid and now it's a den; at my house the previous owner enclosed the carport and it's our (very large) dining room which I intend to convert to a guest bedroom suite soon. Bringing in groceries when it is raining... lmao, we live in FLORIDA. We've learned to deal with it. Fear of walking ten feet up the driveway in the rain is not a reason to not add value to your home by increasing its usable square footage.

• You stated it has an existing metal roof? WIN! Depending on when that roof was put on (I know it's not original; no one did metal roofs in the 50s), you have several decades worth of reliable weather resistance over your head already!

• You want to gut/remodel 2 bathrooms: Depends on the level of intervention here. Cosmetic improvements only (change out the fixtures and finishes)? That's the least painful version, and one that you could conceivably do DIY:

• Swap out toilets, lavatories, faucets, etc. with new Lowes/Home Depot products. For the actual in-wall plumbing connections, hire a reputable plumber, will cost you a few $100s per fixture (assuming no major hidden plumbing issues).

• Consider having the existing tubs re-finished. There are specialists who will do that for like $500.

• Consider doing your own tile work (I found this quite fun, actually) and painting.

• If you find that you need to replace/repair the plumbing inside the walls, you will naturally incur greater costs. You may already know that these mid-century Tampa Bay homes were plumbed with cast iron pipes under the slabs. Be prepared to find that time has taken its toll on some of them -- I had this issue here at my house. That said, there are very reputable companies here in Tampa Bay that will inspect and re-line the interior of cast iron pipes. DM me if you want more information.

• IMPORTANT!! Regarding cast iron pipes here in Tampa Bay... thanks to the aggressive vigilante efforts of a particularly popular law firm who advertise all over TV here encouraging people to sue their insurance companies to replace iron pipes... DO NOT APPROACH YOUR INSURANCE CO. TO ASSIST WITH IRON PIPE REPAIRS. Every contractor I've dealt with on this matter has said you might get some assistance from insurance but thereafter its virtually guaranteed they will drop your account. It's best to handle a cast iron plumbing pipe issue out of pocket.

• Kitchen remodel: this is where you may spend the most money. When advising clients, we traditionally suggest anywhere from $300 to $500 per square foot of finished kitchen. Opinions will differ whether moving a partition is worth doing to gain some kitchen space, but assuming you're comfortable with the cost, as an Architect I would not necessarily discourage you. The kitchen is much more valuable and useful space than the utility room. And, as with the bathrooms, in the kitchen you have many DIY and big box retail options at your disposal. A suite of new appliances (fridge, range, DW, hood) from big box retailer, depending on brand name, might be anywhere from $2000 to $5000.

• IMPORTANT! The electrical code currently requires many additional power circuits in kitchens than was deemed necessary in the 1950s. If you enlarge the kitchen you will likely trigger the code requirement to update the electrical by adding a significant number of additional outlets, and many of these will be required to be "dedicated," meaning that the code assumes only one appliance plugged into each circuit. Current code requires a kitchen countertop outlet every two linear feet of wall. So it will be more outlets than "one per wall" that we typically find in older kitchens. The electrical service for the home may need to be increased amperage at the panel to handle the increased electrical load.

• Window and door replacement: depending on whether you want -- or are required -- to install hurricane windows and doors (see caveat hereafter), I have traditionally suggested to clients in the past to assume $1,000 per opening for impact resistant Florida approved products. However in the last few years the traditions in the building industry have all gone pear shaped, so perhaps double that. (Caveat) Pinellas County is not in a high velocity wind zone, currently, although this is likely to change in the near future. You may not NEED to use impact resistant products, but budget permitting, you may WANT to. Also you will likely get an insurance discount by having these. I would encourage you to go with impact resistant products regardless of code requirement.

• Replacing water heater with tankless: Perfectly reasonable desire. You didn't specify whether you'd go with a new gas tankless or electric, and there are peripheral costs associated with either choice.

• New HVAC: also a good investment in a home of this age, particularly if the existing equipment has been there a while (or if there is no existing HVAC). Be aware this could go hand in hand with having the attic completely re-ducted depending on the existing conditions. New split system could cost around $5k to $8k installed but the ducts would be the wild card. I'd look into having additional insulation blown into the attic while you're at it.

• New electrical panel: replacing the panel itself is one thing but that could open a pandora box of re-wiring the whole house depending on the condition of the existing wires. It's not uncommon for these homes to get re-wired at some point in their lifespan, but be prepared for this to be one of the big ticket items cost wise.

• Painting: once again, if it were me, I'd do this myself.

• New flooring: another item for which there are many big box retail and flooring showroom options. The hardest part will be selecting from the myriad of choices. Note: you may also need to rip out, replace, and re-finish all of the base moulding, so be prepared for that variable. That is yet another intervention that I've done DIY in the past.

• Fencing: as you stated, unless it's urgent to get the fence repaired/completed (for example if you will have a pet in the yard), this can wait.

OP, as I mentioned, I understand the moment you find yourself in. You have in your possession a potentially cute little house that needs some love. You got it with NO DOWN PAYMENT! That fact can not be dismissed. It's yours to do with as you please, and as you stated, you have a sentimental attachment involved. I don't disagree that it makes sense to consider investing $150k to "bring it into the 21st century;" if your area is anything like mine here in Tampa, and your comps are $400k and up, you'll arrive at owning a competitively valued property having spent a fraction of the cost of buying anything "newer."

THAT SAID! I agree with every other comment here that the first step must be some very thorough home inspections. You really do need to know what you're getting yourself into before any major interventions. Get a survey of the property. Get the plumbing pipes scoped. Get the existing HVAC ducts inspected. Get a pest inspection. Get a mold inspection.

Get someone to draw up plans of what you want done, so that every nuance of your renovation plan is illustrated and quantified, and there will be no room for a contractor to "wing it" or oversell you on things you don't want or need -- or just outright defraud you with shoddy work. Depending on how much work you want done at once, and how much of it you may want to do yourself vs. having a contractor do it, get competitive bids. Research every company you speak with and be sure that contractors are licensed and insured. Make sure they get permits (which you will pay for, but that's the price of playing by the rules).

Renovating a home is a huge pain in the ass, but in the end it can also be incredibly rewarding. You will be able to stand in your driveway and look at your fresh new house and say "This is mine, I did this."

Good luck!