So, considering he is the boots on the ground and found this deal for us, what is his reasonable share of the profit?

Airbnb has been extremely profitable for me and the landlords all know I airbnb the apartments.

If that number is less than 250  bucks a unit then it’s not a deal and not worth pursuing 

Count your chickens when they hatch and your profits when you sell.

It's possible to turn a profit if you buy a distressed property and "flip" it to yourself.I bought a 3 bedroom, 1.5 bath with garage conversion as extra living space. 

Doing a high-quality maintenance job by myself for a fraction of what I know I would have to pay a local tradesman (whom I am also sure would do an inferior job, sometimes an unsound job, as a matter of course to maximize his profit and minimize his time expenditure) also gives me immense satisfaction.Finally, I live in a city where outdated yet sound properties in passable locations can be had for very little money, fixed up for minimal cash outlay (as long as you do it yourself), and rented for competitive rates. 

I'm new to real estate investing and I've decided that I want to pursue this as a serious career in hopes that I can one day leave my current job.

Trying to learn how to find properties at a good price in order to make a good profit.

Or how do you calculate how much profit a property will give you? 

Good luck to everyone pursuing cash flow through real estate, it can be done, but it is not easy.