He will be receiving a percentage of our revenue (per deal), so how would that work if I'll be filing Sub S, if he is receiving a portion of the revenue.  

At least you would get a tax deduction on a portion of that money.The key is to not quit your day job while you are exploring.  

For instance, you find a deal yourself, but you allow her to present you and get the buyer's agent portion of the commission.

Although a large portion goes back into the marketing to generate the leads, there is still a lot of money being made. 

This means we would leave our home (legal 2 family with in-law apartment rented + rent out the portion we live in as well) and get the FHA for the cheap down and rehab financing.

And they pay a portion of that which is still cheaper than if they were responsible for their own utilities.  

A lot of times people think they are current, which they usually are sort of, but in actuality they might have part of 2014 yet to pay or they may be paid up to date but they actually will owe you the prorated  portion of 2015.  

I read somewhere that you can write off on your taxes a certain portion of your income if the property is younger than 27.5 years (or something to that tune).

Only the interest portion of your repayment is deductible as a business expense.  

In the multi-verse, you look for tired landlords with tired operations where you determine you can improve the performance of the business, which translates into a higher valued asset.In the residential world (1 - 4 units) your valuation is based upon comparative sales which takes a not insignificant portion of the control out of your hands.