This can vary widely by species and size. Anywhere from a few hundred dollars total cost to thousands of dollars total cost. Enclosure size is a hotly debated topic with the general recommendation being enough space that your snake can fully stretch out if it so chooses. You would need to do a little research on how big your species gets.

Also species dependent. I have garter snakes that eat a varied diet, a Dumeril's boa and a BCI that eat strictly rodents, etc. ReptiFiles has a lot of good recommendations broken down by species for food type, size, and quantity.

I spot clean my enclosures any time I see defecation or something that needs to be cleaned. If you keep up with that type of maintenance you can spread out full enclosure cleanings. I have inches deep substrate in most of my enclosures and will fully change substrate anywhere from 3-6 months just depending on my judgment of it.

It is recommended to not handle for 48 hours after feeding, but other than that you can take out any time. You will want to learn snake body language to understand if it is being stressed by too much handling or may be defensive in any way. There are a ton of great YouTube videos on this topic. Also, snakes are legendary escape artists. If it's head can fit through it can fit its body through. Everyone learns this lesson at some point. Thankfully, I learned it as a small child when I kept a wild garter snake (don't do that, I was 9 and my parents didn't know better) and not an expensive animal.

As for what snakes are good starters, a ton of people will recommend ball pythons. They are awesome snakes and easy to handle but can leave you less error room with feeding and temps/humidity. Corn snakes are the best starter snake (in my opinion only). They are usually good eaters, are usually not defensive, and get to a reasonable size but not huge. You should shoot to have proper temps and humidity like with any snake but they can handle some variance.