This business like any other business it takes many years, blood and sweat.

But the buyer was pre approved through another lender so no sweat. 

This waiting game is making us impatient so we are starting to look at SFH's with high potential for sweat equity (foreclosures, ugly, dirty, compartmentalized, but livable within 2 months).  

Nope, you've been there 5 years, don't sweat it.

But, I'm wondering if I'm really doing the smartest thing with my primary equity.I've considered renting out my primary residence and buying a "new" house to live in and perform some rehab/sweat equity on.

John is providing the capital while the investor is providing sweat equity.

I am looking for my first deal in the central Mass area and will also be putting a lot of sweat equity into it.

Document everything, follow your processes, and don't sweat it. 

In your question, let's say you bought the property for $20K and you begin rehab, cleaning it up and getting it into livable condition when it was not in that condition when you bought it and you spend another $20K doing that and/or you sweat equity with your work and one day before six months runs out the original owner decides to redeem they can pay $21K into the court and get the deed immediately back. 

Lots of sweat equity to get there though!