Hi J.R.
Insurance. List the 'skippers'. You'll probably be asked to anyway and it'll make things a lot easier if there ever was a serious problem.
Re Bank account. We didn't have one on the basis that it's not about where the money is kept but how it's managed that's important. It doesn't mean you shouldn't open one though! Whichever way, appoint a Treasurer and decide how he/she is funded. Develop an annual budget and end-of-year accounts. Keep receipts. Provide for the possibility of unexpected expenditure. Work out a procedure for buying consumables (especially fuel, but also food and stuff if it's a cruising boat). Decide what to do if an individual has to spend money in an emergency - to replace a dud battery or to pay a mechanic. Breakages - "you break it, you replace it" works if it's a cup but not if the propellor falls off and disappears. Don't worry if you don't think of everything in advance. In fact trying to nail it all down tight can be off-putting. Sort out the main items and if the attitude is right you'll work it out as you go along.
Proof of ownership should be shown in some document that everybody has a copy of - your agreement, the original receipt if you buy new, etc.
And a few more things....
Allocating roles spreads the work and makes everyone feel involved. Also there's less confusion about whether something has been done or not. Everybody should be expected to pitch in for annual cleaning, painting, anti-fouling etc but one person might take primary responsibility for maintenance or as I've said, the accounts. Roles can be rotated if you wish.
If it's a boat you'll use individually, it's important that everybody understands what condition it should be left in. It's the small things that irritate most so agree for example to always put things back where they belong! Have a communication system for when you won't be back on time or if there is a problem.
It's largely common-sense and a little forethought!
Pat