We thought about doing seller financing for the $172K but it will likely take 10+ years to pay the full amount at any sort of reasonable monthly payment.

I’m not sure you can reasonably expect that you are going to recoup 70%-100% of the heat/AC costs.

There are numerous reasons why people want to be wealthy.

You can stack your personal 50%s up for separate ventures while still knocking out deals without your own capital2) Read Raising Private Capital by Matt Faircloth3) One LLC with the S Corp designation to pay yourself a reasonable salary from the flip profits.

There's a reason security is there.

Given the size of the asset, these won't be huge, but something to consider.REWARD - In addition to the benefits stated above, the only other reason I could see doing one on an asset this size is if you wanted to offset a property sale that would have a large capital gains. 

The reason not to upgrade, is that you won't get that much more income for the cost of the upgrades.  

It is lakefront so that is an important reason.

The reason I am trying to free up this property is I would like to have an adu built on it eventually.

so I'm wondering if around $50k is reasonable to get a smaller single family home up to speed where it looks something like what you'd see on HGTV.