Hey @Steven Sturman, you just have to factor the interest into your calculations to determine your purchase price. I like to divide my refi amount (75% ARV) by the interest rate. You'll need to convert your 12% interest rate to 1.12 for your calculation. For example...
ARV: $160,000
Refi amount @75% LTV: (.75 x 160,000) = $120,000
Repairs: $20,000
Hard money loan for purchase + repairs: 120,000/1.12 = 107,142
Max purchase amount: 107,142(HML loan) - 20,000(repairs budget) = $87,142
So you would purchase this home for $87,142 put $20,000 into it for repairs, rent it out, and refinance, which will get you $120,000. now you have to pay back your HML with interest, which will be the principal (107,142) + interest (107,142 x .12 = 12,857) which equals....$120,000
Don't forget that even these numbers are over-simplified, as you'll need to also consider other fees your HML might charge, holding costs while you are doing the renovations, and potential closing costs on the refi (unless your bank is willing to roll those into your loan.) I hope this helps!