I just use the tax assessors calculator and it explains all the formulas. 

Here are the one's you need to use to tell yourself which way to go:If you are holding the property, or flipping it, the basic formula is the same...what changes are the specific applications and items those numbers are applied to and come from.  

I've loved learning about different formulas folks follow on podcasts and am excited to dive in and learn from and with all of you!

Basically the example formula would be $75.00 + monthly lease fee (100%) \ 12 months.    

The only thing that can't be forced is time -- the age of the oldest CC is always part of that formula, so it probably does make sense for your son to get a (small) CC that he uses only for small purchase and always, always, always pays on time..

. ** and yes: I don't know how you are arriving at 50k But go see it: based on comparable sales arrive at an ARV (after repair value): then get the estimated rehab cost from a reliable contractor: Then get the ARV $: times 65% : that will give you X: minus repair cost : and that will equal your offer priceFor example: ARV is $100k : times 65% : or 65k minus 20k in renovations: so your offer will be: $45k You can't lose with this formula. 

Here's the airbnb guru:  Brian Pagehttps://imclibrary.com/product/bnb-formula-by-bria...ORhttps://bnbformula.com/enrollnow-main?

NPV=R*(1-(1+i)^n/i )- initial investmentIn the above formula,R is the net cash inflow expected to be received in each period;i is the required rate of return per period;n are the number of periods during which the project is expected to operate and generate cash inflows.But most folks use the spreadsheet to make life easier (see below)Account Closed,  see if using a spreadsheet makes it a bit more clear. if you NPV is different you are probably using a different discount rate, so check that.

I like @David Song observation.  

I want to quickly take an address and figure out number of bedrooms, baths, cap rates, repair estimates, to quickly have a set formula I can use to make offers.