re: Steel wall in-ground pool with vinyl liner

That is the type of pool I have. Previous owners had it installed. So our situations are similar.

I wouldn't expect to get 20 years out of liner. Maybe 10 if you choose highest mil rated liner.

My pool is small. Only 13k gallons. It isn't difficult to maintain. But it's something you do have to stay on top of. I probably spend 500 per year on chemicals.

What type of filter? Most likely will be cartridge or sand. Sand is cheaper requires less labor, but not as effective as cartridge. The cartridge filters aren't cheap. Throw another 250 per year.