I believe his all-in costs for the reno will be $140,000Below is a zillow appreciation map of the zip code in Columbus.Here are some comps (remember to factor in the appreciation when looking at the closed comps)Follow this link to see the page:https://www.flexmls.com/link.h...This link is valid until 10/29/2020.

You're making this overly complicated.Short-term rentals are complicated as is, and have different tax treatment than traditional, long-term rentals. 

Edit:  My father has specifically stated that his age does not factor into their real estate investment decisions (the idea is that I would do all the work anyway). 

If you can hold it long enough to get capital gains treatment you'll save some tax, or better year, get a Roth and do your flips in the Roth... no tax (but leave the money in).

Many factors to consider like - Can the residents afford an increase, are they great residents, am I getting a decent ROI, do I want to create the risk of turnover, etc. 

The Structural bracing, lateral loads, snow drift, etc. require a higher safety factors.

Thus far we have been turned down for financing based on a few factors (by hard money lenders):1.

Expenses are all separate, water sewage(I pay) Is factored in expenses.

I wanted to know roughly how much it would cost so that I can factor that into my offer price, but the various plumbing companies weren't willing to give me a range, they probably don't wanna commit before seeing the place, stating that it depends how long the pipes need to be, how they need to seal up the connection to the well, etc. 

Are there any calculators out there to plug in these factors and see an actual spreadsheet of projected ROI?