massive amount to consider heres a few random thoughts/ideas
size--for me nothing less than 20ft for north sea
inboard/outboard????--outboards are getting more reliable each year.
experience level of the 3 of you ??????? if none join a club,do a couple of charters,get some formal training under your belt,may seem expensive,but so are funerals.
make sure you have adequate maintainance to your vessel,get advice from coastguard on safety issues/equip
do you want a fast boat or an 8knot plodder????
boats are expensive,but but split 3 ways should be a big help the enjoyment levels are massive.
DONT go to the pub to discuss/make decisions/agreements
plan it,and you will be fine---enjoy