It’s crucial to conduct your own due diligence, especially when it comes to rent comparisons and property sale prices.

However, I don’t have a US-based W2 (but work full time for an American tech company in their London office). 

I’d look into the cost of a 500 sq. ft. garage and compare it to the potential boost in sale price.

After doing what I felt was enough research—even though the sales pitch was a bit pushy—I decided to move forward.Their pamphlet outlined several guarantees and provided additional details.

I did check Loopnet and it's all listed for sale by brokers and agents, so I don't think it is off-market -- right?

However, value add with a sale is not as implacted by rates.  

That will put us into the long term capital gains category on the sale. 

If you want to combine two or more lesser sales into one higher purchase that is fine as long as your purchase meets the timing requirements for each sale.  

This home was located in a zip code that is notorious for its ultra-modern design (though those homes are still sitting for sale).

It's still for sale.