I own a triplex and was wondering if I could use one unit as a short term rental to offset my W2 income as a trader business.

If walls are damaged enough to add extra cost to paint job, you can have contractor itemize that part as additional charge and deduct from security.

If your competition is at 60% cost to income, then you should be close to that

With 25% down conventional (full income verification) even with 2+ units rates should be healthier..I wouldn’t suggest investing on the rate so much as the quality of property and analysis.

If I need to undergo a colonoscopy to determine if a lender makes a 30 year loan to people with an 815 FICO at 85% LTV with an in place tenant and monthly income of $1400 with a market value of $125,000, or if you can't tell me any interest rate info until I submit my tax returns to you...

The buyer wanted to double close so that was an additional cost.

We wire money on occasion from the US to PR and vice verse. no tax implications for moving money. or we also use US banks for PR income.

If you want to learn more about the practice (and art) of safely and securely finding and funding a PML to see if it's for you, check out my book on BiggerPockets called Lend to Live: Earn Hassle-Free Passive Income in Real Estate with Private Money Lending. 

I currently own one STR in the mountains outside of Denver and am looking to purchase additional investment properties.  

Section 8 does have challanges but the oppertunity to make multiple income streams and even expand your real estate investmets can become much greater.