I suggest find your self a good Lawyer, and an Accountant,  Talk to them before making any decesion, with 8 different oppnions, it is good to spend the money and talk to the professional as how best to structure it, entry, exit and other conditions, must be agreed amoung all participants before you go looking for properties. Ask all the questions such as the above they will best be able to answer your questions on the spot.
Partnership is too risky. Good Luck

Hi, I think you dont know your price !, yes first you need to research the area that you want to buy in and the rentals you can expect, than work out how much you want to spent  on the property, ( ie that is the price of the property ) depending on your own situation ( tax etc….),  than only  you will know how much deposit you need, 10% for investment property should be ok . Good Luck