It really depends on what kind of investing you plan on doing. If you are going to be a land lord you and your partner will need some protection from liability. If you have specific property, duration, etc. a joint venture might work for you. If you are buying and selling paper, etc, you may seek another form. It will also depend upon what forms of organization your state recognizes. In my state you don't need any paper to be a partnership, just call yourself that and that's it (never a good idea). You will probably want to talk to your accountant for tax ramifications and your attorney for organization.
It really depends on what kind of investing you plan on doing. If you are going to be a land lord you and your partner will need some protection from liability. If you have specific property, duration, etc. a joint venture might work for you. If you are buying and selling paper, etc, you may seek another form. It will also depend upon what forms of organization your state recognizes. In my state you don't need any paper to be a partnership, just call yourself that and that's it (never a good idea). You will probably want to talk to your accountant for tax ramifications and your attorney for organization.
Definiteluy talk with a CPA and Attorney! You want to have everything clearly spelled out Beforehand.
Good Luck!