I think this is just going to come down to you, are you ok with having a mentor that will take 50% profit from all your deals?
If anything, weigh your pros and cons: What are you learning from this guy? Is he bringing you valuable contacts that you can personally use later down the road to pursue more deals? Is he helping you set up proper structure and a business plan, or at least a plan of attack to become a well rounded company that can pursue investments while limiting risks? Is he setting up the deals, and bringing in buyers and simply teaching you how to do the same; or will he use you and the deals you set up, while taking 50% profit because you simply call him with a question here and there?
If the guy is doing great things to help further your progress, increase your contact list, and he will eventually make you self reliant in the future to do your own deals, then with all things considered why not? It may be better in the long run than if you didn't have any help or guidance.
That being said, i don't agree with a mentor that want's 50% of your profit, and for the next 10 deals or for 6 months.. I agree with paying for a mentor for lets say couple thousand bucks for 6 months of help, and a cut off deals that he helps bring to you. Weigh out what this guy brings to the table, and if it is really important; if he is setting up the deals, and bringing in buyers while you do some work, but showing you step by step how to do the process, and learning along the way - than i think it might not be a bad idea, depending on how comfortable you are with Real Estate right now. But if he want's 50% of the profit for the deals that he has no influence with, than he should not have the right to say that 50% of that profit is his. Just as you may hear on bigger pockets podcasts, there are lots of people out there who want to make a buck, and lots of people out there who just want to help. if you determine that his guy doesn't have your best interest at heart, and wants to profit from deals he didn't help create, then maybe find another mentor. But if you feel that he brings lots of value, and can help you get on your feet and pursue more deals in the future while bring you deals to pursue right now, than it's not a bad thing, as i feel everyone should get paid for the efforts they put in.
Hope this helps! Good luck