I spent some time talking with a guy who’s a 1/3rd owner of a 2003 Cirrus SR22 at a local airfield’s open house last weekend. (It was in beautiful condition - you’d never know it was a 20-year-old plane. Previous owner apparently had it in southern Utah, which helped keep it in tip-top condition.) He told me that the three of them chip in $650 a month, which covers insurance and most maintenance. They do a lot of the basic maintenance work (oil changes, etc) themselves. They “bill” themselves a rate for the flight hours each of them use, which also goes towards maintenance and fuel costs. I think they paid about $250k for the plane a couple of years ago. (He said a new SR22 would cost you about $1.3m, and there’s a 4 year waiting list for them. That surprised me - I didn’t know the civil aviation market was that robust these days.)
I also had a client several years ago who bought a Gulfstream for himself (a IV I think). I wound up excessively involved in that process, and all of it taught me one thing: if you want to make a little money, make a lot of money and buy a jet.
(And I never even got a ride on the dang thing!)