Charlie,
Not experienced with partnerships, but am a little with LLCs. As always, definitely get an attorney as they are pretty good at legal things....
1. Yes, most definitely. An LLC has an operating agreement by which you lay out the agreements of the business members. You can explicitly handle ALL situations here from % ownership to capital investment to managing partner, etc...
2. My understanding is an LLC is a good entity for small real estate investors (sole ownership or otherwise). Most of the reasons are for tax purposes and overhead of management.
3. This is more a financing/lender question. There is a lot of info out there on mortgages with LLC entities. The general issue arises with the due on sale clause on mortgages. Basically a lender will not mortgage a property under an LLC for competitive rates. They will do it, but since it is higher risk the rates are higher (there is also a factor of how long the LLC is in business). So if you mortgage personally and then try to put it in the LLC the bank could call the due on sale and require the mortgage to be paid in full. Past getting a business line of credit I am not sure how you would go about legally holding a personal mortgage between the two of you.
4. Not sure
5. That is something you specify in operating agreement. Be explicit.
The best piece of advice I give you is talk to a lawyer. the amount of value you get from 4 hours of consultation is worth it. Even if they just give you a solid op agreement since that seems like it would solve a lot of your questions. Think of it as part of the cost to buy a property.