You lose the ability to put it back with a complete demo in some areas when it is non-conforming. 

Speaking from a Contr's point of view, I would not want to install anything that a homeowner purchased. a) I lose out on the material mark-up, b) if there is a failure, you're going to call the Contr regardless, right?

If you let a unit go vacant for a month you'll be losing potential income and actual money when you have to pay the mortgage out of pocket for that month. 

((Best)) way I can think of is have some money to invest and partner with a more experienced developer who is doing what you want to do.Come in as a Jr. type partner in the deal, and work full time at it--learning.By Jr. type partner I mean you are not calling the shots, but are in on all meetings and all aspects of the project.After a few deals maybe you want to go it on your own, or maybe just keep on partnering....A good partnership is a definite strength--but it depends on the person.I would say that is the (BEST) way to learn a particular development type.If you lack meaningful money try befriending a few developers and just talk shop as well as friendship things, and see what turns up.But to be a developer you will need to have a good sized chunk of change to risk (possibly losing) to do a deal.Good Luck!

Get some help to ensure you don't lose your money.

Do I lose my 3% earnest money? 

Think he ended up losing his license.

But that might not be a big enough carrot if he’s going to lose out on $50k/year in rent.

Surprised since it flooded in June 2021, but it seemed like he "learned" by trying to get rid of it ASAP after June and didn't expect another major northeast storm to cause even worse damage before the house closes in 2 weeks.I too agree with you that the probable good +cash flow will not be worth the headaches/possible loses down the road in the long run. 

You can buy houses with credit cards, but have to convert the money into cash, which costs many percentage points (unless you have a special offer from the specific CC), but once you convert to cash, you lose the points associated with spending the money.However, I do run all of my rehab projects through credit cards, and frequently have tens of thousands of dollars running through those little puppies.