Not much experience on that, but to start the conversation...
Sounds great as long as you are OK with the idea that half of that apartment will be his aaand you are certain that you are in a healthy relationship.
By the way, now that I think about it, there should be one person the lease is signed for and if the name on the contract is yours then you can be calm possession-wise. In the future that is. And as for paying the lease... well, if you are confident that you can start a company with that person, then a lease will be no match for you:)
Measure his financial 'strength' so to say. I wouldn't share an apartment lease with my girl if she was a waitress or changing her job twice a year.
Not much, but from heart as people say. Hope this gets your mind in the right direction.