I'm going to be yet another that says to avoid a partnership...
I've also been another grower that has embarked on a partnership with a family member, and it ended in bitterness. Long story.
Recently I decided to break my rule. I wanted to expand, and an older, solid, established friend of the family approached me with a deal. He had the property, a couple large containers. He would fund the build out of both containers, while I design and help build. Once finished, I would be able to use one container to myself, elec/bills paid, I prove supplies, keep 100%. The catch, that I teach him the ways of growing cannabis. He's a very smart, solid guy, with agricultural experience as well as every other damn trade it seems. So I weighed my options, and with some of my time opening up I figured what the fuck... Well things started to get rocky from the beginning with an estranged family member of his that had a stake in the property, so I immediately backed out in the early stages once I came to my senses.
It's a VERY small percentage rate of partnerships that work out in these endeavors... You have to have two, honest/trustworthy solid guys, matching personalities, goal-driven without greed, matching goals with mutual, realistic expectations, no strings attached to other people/things that could bring potential problems, etc etc. That's hard to come by in today's world.
And my point is... even if you find somebody with those qualities, having one other human being involved instantly doubles every risk possible... The only person you can trust 100% with money, and most of all, freedom, is yourself.
And this goes for whether it's an investor, or an actual straight up 50/50 labor/profits agreement. The latter being a bigger risk.
With all that being said. If one were to embark on such partnership with strictly an investor, 50/50 is proper but... Usually the way this works, like my dude mayo mentioned, is it works more like a loan with royalties... and that would be the most likely to pan out.
If you can do the same thing yourself in 4 months... back down from the plan with your dude. 4 months is nothing... just be a bit more patient, work hard, and big things will come your way.