Your son is responsible for making payments on time or ruining this seller's credit. 

I have a 2.5% interest rate on the balance of the mortgage. 

Sourced through the MLS and negotiated heavily with the seller to get price reductions and credits at closing How did you finance this deal?

am working with them now and had the first policy (with Spinnaker) cancelled for nonpayment/late payment so we rewrote another policy (with Millenial) and having the same payment problem again but at least they are communicating that cancellation is coming. they want me to pay by credit card over the phone so the payment wont be late and cancelled again. but when i go to mycoverageinfo.com to check on status it shows its been paid.

When you tell them they will only get paid when the loan closes, they will disappear.If required, the only money you should ever send to the lender is for a credit check.

Appraisals came back awesome my credit score came back 720.

Keep your payment at no more than 35% of your income and minimize your credit card and auto debt.  

The fees and rate are generally higher on DSCR loans. 

The most important rule is to have the cash flow of the new property be able to pay all its expenses, mortgage, AND the line of credit back.

(May also cut significantly into the current cash flow on it)I know you mentioned not doing a HELOC on my primary, but wouldn't it be advantageous to have the ability to pay off the line of credit instead of be stuck in a payment that is much higher?