What is the best way to track this and "earmark" those funds for that category in the Quickbooks program?

If you only have 1 property to keep track of every month, I think a simpler solution is warranted (I don't have any rentals so feel free to correct me).  

Also frankly any place fairly close to Waltham will be the most competitive of the whole range you are looking at so, while a good deal will sell instantly, it will be that much harder to find a deal starting out.I think you are on the right track with the Nashua area.  

She already has a spreadsheet set up to track rents payments and payments of the water bill by our tenants. 

You just gotta look at whats going on in the market, including how long it takes things to sell, what other houses have sold for, if there are things that make this house more valuable (views, acreage, nicely renovated, neighborhood amenities, etc) or less valuable (steep driveway, on train tracks, trashy neighbors, in a flood plain, etc.) and use some common sense on what people will pay more or less for.  

In the software business this would be a "bug tracking" system.  

Looking for a good excel sheet - not to complicated, to keep track of 10 rents on one property. 

We get about 25% back too but we track the owners down and call them to make offers.

We don't track the exact numbers because this is something we do part time while working around our full time day job. 

In fact right now we are refi'ing through a 3rd portfolio lender who gives loans based on the asset which is unique.What helped us obtain the refi's I think was our track records and the fact that the properties we bought were good deals and attractive to a bank to refi.