If you can afford to buy an airplane, then the M20C is a great alternative to either a 172 or PA-28. Similar acquisition cost, practically the same engine, and if it has manual gear and hydraulic flaps, nearly as easy to take care of as the Cessna or Piper.
Of course, this doesn't take into account any gotchas like corrosion or bad engine- but that could happen with the Piper or Cessna, too.
Maintenance will be 10-15% more in the M20C, In my experience, less if you can work with a knowledgable A&P and do a lot of work yourself.
Insurance will be significantly higher until you gain experience in the Mooney and get an instrument rating. Just a guess, but insurance for the 172 might run $1000/year, the M20C would be $3000+ for the first year, $2500 the second year, $2000 the third etc.
This may be a good question to ask the group here. If you can afford the insurance, get the Mooney.
One additional item to add to your budget- pay $75 for a small refrigerator so you can have cold beer for your hangar. Best way I know to make friends and get help with maintenance.