If I buy for 325k, put 105-125k into it and sell at 575-600k, I'm good with that margin as we've proven it works, have a grasp on that market and hold time, and floor price. 

I would suggest a person who has a track record to lean on seek portfolio lending, in that instance it is up to their internal policy for such and even then a deviation can be requested and they meet, discuss, and let you know. 

What is the best way to track expenses and make tax season easier?  

Send it certified mail so you can track receipt.

You're on the right track as long as your lease has been vetted with a real estate lawyer which actively practices in tenant/landlord litigation, again actively practices - very important - just ensure that is balanced, if it's too landlord friendly that's not good either but your attorney will be able to find that balance.

A track record is important.

I guess I’m kind of already on the right track.

Once you have a track record or you pursue private equity a waterfall is more common place.

Also, they seem to have a great track record for finding top-notch tenants - and that’s worth something too!  

This requires him to keep track of hours and expenses but would ensure he's paid more for properties that take more work and paid less for properties that are easy.The first option is my preference because it requires less effort on everyone's part.