And if you do ruin the relationship, it can ruin it between you and the stepson, as well as with many other family members.It also looks like you're trying to buy a rental that works for his budget, not one that makes sense for you as an investor.

When you begin creating a budget for the renovation phase, add an additional 10% as a buffer.

Then they wonder why their project shows $3,000 - $5,000 over budget after they've counted up all their remodeling expenses.

There are no “average” rehab costs as every project is different.Ok, so when you can lock in an exit value, a rehab budget and your offer price, we can then see if you have a deal worth doing or not.Ball in your court.

Just make sure to budget for higher repair or cap ex.

I would then budget 3% or less.

I learned a ton of lessons, went over budget some (expected), but I’m even more motivated to move on to the next.  

I would budget to be at least 7 years into the deal. 

Don't start moving the goalposts (i.e. by inflating the sell price or lowering the reno budget without data to support it; using 80% instead of 65-70% in the equation above to sacrifice your eventual return) in an effort to wedge a square peg through a round hole.Not every property you analyze works, and providing them with a "low" offer isn't taking advantage of them. 

All of your reno ideas are kind of low-budget, so why bother?