Fix and Flip Calculator Issue

[Michael Coffey]

Hi everyone.  I just recently found BP and this is my first question.

It seems that one of the main purposes of the Fix and Flip calculator is to determine what your max allowable offer should be based on ARV and profit. And yet the calculator needs to know what my mortgage monthly payment is. Don't I need to know what my purchase offer is before knowing my mortgage payment? It seems odd that I need to know what my offer is before it tells me what my offer should be. Perhaps the calculator should have a mortgage section where you input your expected interest percentage and # of years instead.

On a side note, if I'm expecting to live in my fix and flip, lets say for 2 years and then sell, should I be subtracting what my current rent is to understand my overall bigger picture?  For example, if I'm renting at $1,000 / month but I move into my newly acquired house soon after, does it make sense that I should be able to subtract the money I'm saving from not having to rent an apartment?

Thanks for any help!