It is one reason most LLs will not accept CCs for rent payments.

So can I calculate my cash on cash return like below $40K(appreciation)/($42k(Down payment)+(2.1K(Monthly payment for Mortgage+HOA)*36)) = 40/(42+75.6)= 34% so the annual cash on cash return is about 1.34 to find the cubit root.

Hi Brad, I believe a 401k loan may be helpful in terms of putting toward a down payment if needed. 

Cash available: 100k

The triplex is occupied and currently bringing in positive cash flow.

Your suggestion would be considered a negative cash flow investment.

Who's asking for the down payment?

There are two types of return from a rental propertyCash Flow & Appreciation.I normally also aim for a minimum of 8% return between Cash-Flow and Appreciation.Appreication, nationally, is around 2% to 3% annually.Therefore, your goal is to get the cash-flow to be about 5% to 6%.The issue is interest rates being very high, you would therefore, need to buy at a pricepoint where the numbers still make sense.You can always put down more of a downpayment to cash flow, but that will impact your cash on cash return calculations.Best of luck!

So I'd be pulling equity at 9% and only get paid 5% if I used the HELOC and kept the cash in my high yield account. 

In this case, since they are borrowing their payments, these would get added to the principal balance each month, and interest would be calculated on that.If, for example, the interest rate on the note were 10%, they would implicitly be borrowing their payments at that rate.