Fonsini
I have read your OP together with the subsequent posts.
May I suggest that you consider the following :-
a) Seek an aircraft that fulfils your mission profile and budget (including
operating costs).
b) Upon purchase of said aircraft, set up a flying group.
c) You may deposit some money into that flying group for operating
expenses and suchlike.
d) You may, or may not be able to sell any 1/20th shares in the aircraft but I
am quite sure that you could convince your flying buddy to buy a share.
You may pay your flying buddy to wash/valet the said aircraft from time to time.
Your flying buddy may even invite you to Phoenix and Vegas from time to time on days that suits your own itinerary.
I'm not a lawyer and that advice is worth as much as you have paid for it.