Which you can also try if you win with your super low bid. 

For example, I am in Dallas, TX - the cap rates are very low here.

Possibly house hack as well but the low rate is worth more than finding a "deal."

And the price to enter is extremely low compared to other markets in the U.S

That seems very low.

Is vacancy low and they plan to lease it up?  

As soon as there is no more money left (or it's low), you must contribute again.

I've had several bids, all much higher than the original, unrealistically low contract price, with of course a lot of variety in the price, experience, and track record of various builders.

These things hold their value amazingly well.If I had to guess, if you bought it for 40k and only used 9 or 10 times, the hours on the machine would be so low you could probably resell it for 35k or better (given that their retail value would go up over three years so the discount from say 48k to 40k might even mean you break even)..

It is all dependent on the numbers.If you are planning on putting low money down, the odds of it cash flowing (or even breaking even) in the first year would be difficult.