Well this is a very open ended question. For £2000 - £3000 the aircraft will depend on how many are in the group. With 4 or 5 in the group the only 4 seater that would probably be possible would be a tired Cherokee, with 12 in the group then you would be in the £35k range and could, maybe, get something half decent.
It does depend on the number of shares. The fewer shares then (generally) the higher the availability and (probably) a better looked after aircraft, the more shares then the lower the unit cost per member. I know this is fairl obvious but it does make your question almost impossible to answer.
I believe the legal maximum is 20 members - which at £3k a member is a £60k aircraft - with 2 members it is a £6k aircraft.
Monthly costs are usually somewhere between £50 and £150 depending on aircraft. whether it is hangared or not, how much is going into a contingency fund etc. etc.
You don't get owt for nowt