built into rate for my fees -Interest Only payments for 1st 18 mos.

Spend that refund on than the down payment on another house to use for bonus depreciation next year, which generates a big refund next year, which you can use for another down payment the year after, which generates another big refund the year after.

Big down payments. 

House-hacking of some kind in Denver will allow you to buy with less down and get most of your payment covered by others, allowing you to save for the next. 

Sure you can use a large down payment to evade that PMI, and this will boost the cashflow per door.

I'm hoping to build a network of wholesalers that are reliable that I can consistently lend to for transactions.

I've most often seen it with sellers who aren't interested in doing a 1031 and they save some on taxes, earn interest, have a swtream of payments, but no obligation to operations/maintenance. 10 years or less is likely.

On the other hand a line of credit might work for the down payment, but you will likely want to look for a private or hard money lender for the fix and flip portion and as a beginner, I would expect to put between 20-25% down and likely a bit more for closing costs and reserves. 

The funds supposedly earmarked for these payments were instead usedto cover its debt repayments.

I haven't done a down payment since 2015 and have 9 doors including my personal residence.