And here's why:
Normally most people think a partnership is a good thing when it comes to co-owning. But in the case of starting a business, as someone suggested, you open yourself up to unlimited liability.
Why?
Because when you file the least expensive form of partnership, you end up with a general type of partnership. General partners are able to put the entire partnership into debt, and each partner is completely liable for the debts of the partnership.
What does that mean?
Partner A and Partner B come together for a business deal. They go to the local municipality or county recorders office and file partnership paperwork under a "fictitious business name", also known in other places as a "doing business as" name.
Partner A is cautious and proceeds as agreed upon. Partner B is a risk-taker, and signs the partnership up for all types of debts using his/her signature only. Logic would have you think that only Partner B is liable for what he signed the partnership into. But the law says otherwise.
Partner A finds out and disagrees with Partner B's risky behavior and spending. They argue (it's a partnership, it could happen), and Partner B splits. Neither Partner A nor the creditors Partner B has signed the partnership into debt with can find him.
Guess what?
Partner A gets sued by the creditors and is required to pay the debts, even though he/she did not even sign the paperwork.
The legal logic is this:
Either partner can sign paperwork putting the partnership into debt all by him/herself, and the partnership (and therefore all partners creditors are able to find) is completely liable for the debt.
By the way, I'm not a lawyer . . . I learned this by picking up a copy of a book written by one of Robert Kiyosaki's (Rich Dad Poor Dad) advisors.
There are other types of partnerships that offer more protection, and other types of entities besides partnerships that can have both more protection and more flexibility.
All I'm saying is, before you jump into a partnership PROCEED WITH CAUTION.