I know there are probably some other factors and variables at play here, but if you were in my shoes, what would you do?

Downside is that the rate is variable, and there is a chance that it may get frozen exactly when you need it most - when real estate prices crash and there's good deals to be had left and right (a la 2008-2010).

I am also not sure that $100K houses are the best investment. if you can manage it - that's definitely one of the variables to take into consideration!

With the major variable of Covid it's hard to accurately predict anything right now IMO.

There are a lot of variables with old houses.

Is there a database or guide that gives a price to each of these variables?

I'm curious if you're still marketing to all those niches you mentioned, and if you're seeing any variability between them or between markets on seller motivation.We've made some attempts at direct mail marketing and talked to many potential sellers who would take no less than way more than what their property was worth… many seem to have eventually sold to other investors, and I'm not sure if those investors were just better at talking them down or content to operate on verrry thin margins.

Maintenance, Capex, Vacancies, Lease Ups, Insurance Requirements, and Management Costs are all variables that will widely change the DSCR calculation.  

I have an idea of how much I want to offer, I have good comps and understanding of ARV, but estimating the cost of repairs is the variable that can be off by tens of thousands of dollars if I don't see the property inside.

If you do not want to do that you will have to put down 25% and then at that moment the 75% income variable comes into play.