More ARV formula explanation please

[Joel NA]

I religiously use the ARV x 70% - repairs formula for any flip that I look into. Completed one last fall and made money. I 've only been looking at cash buys and under 100k houses up to this point.

Because of my wife and my w-2's, we're able to get mortgages now. I'm having trouble analyzing deals with this new wrinkle.

Example:

ARV 185K
Repairs 28K

185K x 70% - 28K = $101,500 Max offer

But when I play with the numbers more, I see that down payment, repairs and financing (holding and money costs) come out to just over 52K. So if I bought this house for 125K, I'd end up with a profit of:

185K - 55k (adjusted holding and money cost based on higher purchase price) - 100K (mortgage)- $11,100 (realtor) = $18,900

I'd be happy with almost 19k in profit. The ARV and the repairs are both conservative--ARV could be more based on comps and the repairs could be less. I'd be financing the whole thing through a private loan at 6%, an equity line and other credit.

I know there's mistakes in my reasoning and perhaps my math. Please point them out.

Thanks in advance!

Example