Hey Hayley,
Very interesting post. Unless you are 100% transparent with your brother and you are open about each other's weaknesses and strengths I would not do it. If for any reason either of you cannot uphold your end of the bargain, will the other side be ok with it? Also, considering this is his first investment, who knows how he will react to it. He may hate it and want out right away. He may also love it and want to invest more.
Also, why is he unable to house hack on his own? Why can't he do it, lack of W2 employment, bad credit or etc? If he is only a year or two away from obtaining a house hack, then let him wait it out and invest when he can.
Last option I can think of is you both forming and LLC together. You would need an attorney to make sure everything agreed upon is official. This may present a nice balance of him living as if he were house hacking by limiting some his housing expenses while you may see some benefits such as rental income, loan paydown, and appreciation.
I have a younger brother who I would love to get into real estate but would never invest with him as we have two completely different mindsets. In the end its all business and your money. Just because someone is family does not mean it makes it a better option.
Not sure if that helped or made it more complicated but wising you and your brother the best.
Good luck!