I bought a C172K back in 89' for $22,500. It had a factory rebuilt engine with 35hrs., new interior, decent paint, fresh annual and was certified IFR. I used it to build time and to get my instrument rating. I sold it a year later for $23,500. I then bought a C152 for $17,500 and used it for training. Two other instructors used it for their students as well. I charged $18/hr. for my services and $45/hr. wet for the a/c. I paid $250/mo. to the bank, did owner assisted inspections, paid $2,300/yr. for commercial insurance and paid $80/mo. for a tie-down spot. After about 475 hrs. of dual given I leased it to a flight school for a year and averaged about $1,100/mo. in extra income. I finally sold it for $23,000. It was definately a risk, but I managed to get through it all without any costly unscheduled maintenence.