You may be safe to get non-commercial F/F adding up to 2 ADUs to a duplex even though by rule this does not qualify (in my area I have never heard of this being an issue). 

If you aren’t saving the money up to buy another property chances are nothing will pay a higher rate than paying it towards your mortgage.

I'm a new real estate investor and I recently picked up Brandon's book "Rental Property Investing"..

The last few STR deals I closed where my client used a second home loan, they ended up putting down 20-25%, preferring to have more equity in the property versus giving away thousands in fees to the lender. 

I’ve seen so many investors hesitate because they wanted the whole deal to themselves, only to end up with nothing because they didn’t compromise.🚀 Lesson: A piece of the pie is still better than staring at an empty plate.2.

Look them up online, call and interview several of them.

I have 3 accounts per property which helps me leverage APY on savings accounts, prevent funds from being comingled, and easily set up auto payments for things like mortgage payments and utilities. 

@Roger Kim If your friend qualifies for the Section 121 exclusion, he can exclude up to $250K of capital gains, but gifting you the proceeds won’t legally avoid your tax liability.

You might have other options to explore to drum up liquidity (HELOC, Margin Loan, Policy Loan, etc) that can supplement your HYSA in the DP.

I had to look up what "variance analysis" meant.If I understand the question correctly, you're asking "What went wrong to not hit our 20% target?"