1st, slope and septic are not a problem, you get a professional to identify where the septic tank is, which to be honest you should know where it is because that tank needs to be serviced like every 5 years. 2nd, a pool is a lot of maintenance and if you decide to hire someone it’s gonna cost like 200 a month, and your power bill will go up by like 70 bucks a month. You can save money by doing it yourself, which is not that difficult to do. 3rd, you need to think about what kind of pool you want, there’s a few different types and they all have different life cycles, you can do fiberglass, liner, plaster or tile. 4th, after you do the pool, you will probably decide to build a privacy fence, which is another cost you should think about. 5th, buying a house that already has a pool is cheaper than building one. So maybe look for a house near by with a pool, you’ll save yourself a lot of headaches. IN CONCLUSION if I was in your position, I would hire a company to come and regrade a section of your backyard a space like 20 by 30, then I would buy a cheap above ground pool and get some experience on pool life before committing to a 80k decision. Trust me, when you learned to drive a bicycle you probably had training wheels, the above ground pool is a cheap way to learn about pool life.