Should I go through with taking ownership of the property and try to salvage it for profit or do I refrain from even involving myself in the situation as it may cost more than it's worth to save it?

As you are partnering with your sister, have a legal document drawn up as to what happens if one of you wants to sell and the other doesn't, how expenses will be split along with money you are putting down, borrowing, profits, etc. 

In construction, there is only so much you can do to reduce your margins while staying profitable.

When the time came to sell, I anticipated a solid profit from the deal.

So back to being a real estate investor: the only way to be one is to buy a property and create value out of it, whether through finding a below market value house and selling for a profit, or renting and creating cash flow.  

I've never heard money/profit described as cute, so it's not important.The most important thing you mentioned, was the rent potential and ARV. 

Sold it for a profit fairly quickly.

Cash flow is great, but it can feel incremental compared to the boost you get from equity plays.For me, it's more situational.

A mortgage lender can help determine if refinancing or tapping into equity might allow you to acquire additional properties.Consider a 1031 Exchange: If you're open to selling a current property, a 1031 exchange can defer capital gains taxes while enabling you to upgrade to a larger or more profitable asset.

Offer aid and housing options if you're able -- don't try to profit.