I'm at the end of this process myself. Bought a 172 a year and a half ago. Flew 300 hours, will sell it after my CFI ride in 2 weeks. The loan payment is $220 a month, tie down is $25 a month, insurance $600 a year (was already paying $200 for renters). The variable is maintenance. My recommendation is to find a good freelance mechanic not tied to a big shop. My first annual hurt. Large shop, $3700. Second annual I did an assist with a mobile mechanic, paid $400.
Make sure the plane has IFR avionics, but keep it simple. Lots of extra cost to have a GPS in a plane. I have a single SL30 nav com. I'm not flying hard IFR in it but it was enough to get my instrument rating. When you go commercial, find a cheap twin to rent and use that to knock out your complex time instead of paying for a TAA.