But in general with turnkey the trade off is usually a lower return for not having to fund a property yourself and doing the rehab etc . 

My issue is that I do not have tax returns to get another loan for my next property, but I have the money for my next property.What would you suggest for me to get my next property?

Here we are in 2018, approaching or at the top of another cycle, and they still own the house and would now like to sell in hopes of finally making a small return.

Let's assuming that after backing out commissions from a sale at $520k, I use that since price since that would make it a 6.4% cap, then I net a gain of $155k, then I'd need to target a cash on cash return of 6.1% or higher (my current return on equity). 

@Marlon Long it also could be that you asking price is the only one where investors could get a sensible return compare to most of the folks who thinks 3%-5% is acceptable return and jack up the price as such. 

What are a few ways to estimate how much money needed to put into rehab to get the highest return back at selling?

What is your return? 

My costs go up every year in taxes, insurance, costs of repair, HOA dues, etc.. if you choose to, then definitely include something in return.  

I am looking to stay below 60k and looking for some reasonable cash on cash returns. 

Typically the lender would get anywhere between 8 and 15% return on the money he is lending you just like a hard money lender.