House hacking and cosign with family member

[Cesar S.]

Hello BP, I have a question on house hacking.  I have a family member,  who's single and looking to buy a multi family property (his credit is  670 but mine is better 790).  He has the down payment and closing costs money but may need help depending on property price.  Also, I would need to help him choose the property and run the numbers since he's a newbie.  My question is can I help him by being a cosigner for this loan while he's the primary owner occupant and will he still be able to only put 5% down?   I would be on the deed as well and we would also split any rental income 50/50 since I'm cosigning.  I want do to things the right way and make sure I'm following the rules hence my question.  Thanks!