as helocs go for around 10% and the new rate could be 7% on the cashout refi.

Ditto to all of the above.  85% is very doable with a strong credit score, strong dscr, but yes, the rate is going to be higher because of the higher leverage.

I was just quoted 8% on my heloc, if that helps you at all with getting an idea on interest rates.  

The most reliable way is look at other STR's in the area and see what their nightly rates look like over the year and look at their occupancy rates. 

(a) market price appreciates at a compounding rate AND so does (b) rents appreciate at a compounding rate.   

If you refinance now, you may be limited to a rate and term or delayed purchase (depending on the lender) or pay higher points/fees/higher rate using a DSCR loan without a cash out seasoning requirement.

The reason is that for most programs anyway the 60% loan to value will give you the best rate and best cost available and of course you should still be able to have a healthy cash flow at that loan loan to value.

I've recieved many quotes and preapprovals and they came back with the most competitive rate and terms for what we are looking to do.

10% is a great rate.

Mortgage Balance: $430,000 Monthly Mortgage Payment: $3,100 Current Rent: $4,100/month (below market rate, planning to gradually adjust it during yearly renewal to eventually catch up to the market rate) Appraised Value: $900,000 (purchased for $657,000 8 yrs ago) Managed by a property manager Loan assumableProperty B: Located in VA.