Part of your monthly rent would go to principal reduction.  

We know being an landlord is a job, but if we hold it for long time, it can be a decent income.However, now we are thinking since the interest rate for our sfh is 6.375%, why not sell the townhouse and pay the principal of sfh?

Yes, an entity can be appointed as attorney-in-fact for an individual.My concern about the above... an attorney-in-fact depositing the funds of the principal into their own account would be an obvious breach of fiduciary duty.

My experience so far has been positive.  4 investments starting ~ 9 months ago.  1 completed with principal returned, others are in progress. 

Your mortgage is not only sucking interest, but also principal.

Even with a 5% down payment you are looking at a $2,494.00 a month principal and interest.

Since this is a DSCR loan and I already provided account statements with proof of funds and my mortgage statement for the principal residence, I didn't expect much more would be required.

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23If a purchase, you also generally need reserves / savings to show you have 3-6 month payments of PITIA (principal / interest (mortgage payment), property taxes and insurance and HOA (if applicable).

With real estate, some of the biggest pluses aren't seen in ROE (or ROI for that matter, at least until you sell), namely appreciation, principal paydown and depreciation as a tax write off.

And you’re still getting principal pay down.