If it was in good condition would you keep it, and continue renting it? Or, were you ready to sell anyway?
If you were ready to sell, and you might not get the $30k back if you fix it up, then selling it to the flipper sounds reasonable, and less hassle.
Another way to think about it is, let’s say you can make $20k more if you invest the $30k, do you want to do it? Or, is it still not enough for you to bother? If you wouldn’t want to make the effort even if it was fairly guaranteed you would profit more, then you really have your answer.
Remember you will pay capital gains tax on the sale, unless it was your primary household recently, and you only rented it two years or less. It’s a low tax, but still cuts into your gain.
@stanleybmanly She didn’t say the house is worth less than $30k. She said if she spends $30k to fix it up, she may not get that money back.