You can refinance sooner than that but you'll need to paper trail all of the improvement costs that lead to the increase in value.

We can't HELOC due to TX regulations and cash out refinance doesn't make sense with interest rates.

I am currently investigating taking a cash out refinance on one to fund my next purchase.  

This way you can refinance out all of your cash and hard money positions.Whether or not it will "cashflow" has nothing to do with BRRRR (except for maybe "repeating"!). 

Is it possible to re-finance these separate properties as a group in a single loan?

You could always later cash-out refinance for your next deal too.  

These programs very commonly involve restrictions and conditions on use, refinance, or resale of the property. 

What you have done is effectively refinance your mortgage at a lower, albeit variable, rate.If you go back a couple of years in this thread, I posted a series of spreadsheets comparing variations one of the cases originally presented to sell this approach.If you were to model making more frequently (i.e. accelerated bi-weekly) mortgage payments and augmenting these payments with additional principal payments (the amount you currently apply to the HELoC), my conjecture is the gap would be rather narrower.

These deals are so highly leveraged that if they fail to attain their projections and cannot refinance the project, it will fail and go to zero.

We purchased with a conventional loan, 10% down payment:Purchase Price: $405,000Closing/Fees/Misc: $12,500Repairs: $85,000ARV: $575,000I was hoping for rates to come down some in the next year and refinance out with a 75-80% LTV.