I did it for a living, since the mid-2000s and stopped about a year ago. It in a tough way to make a living, and in my market area, the answer to your question is no. However, that is in a depressed market where there is very little spread between new spec. homes, and clean newer resales. I generally grossed 13-18% of the sale. This is a result of being the GC, electrician, plumber and tile setter. Two other factors weigh heavily, I provided all of my own capital, free of interest costs, but at a steep opportunity cost. Second, realtors were a necessary, but costly part of most deals.
There is no right answer to the question. There are some markets where there is a total killing to be made, and others where you're going to get your ass handed to you. The one point that is nearly universally ignored by newbees in this adventure, is that being a builder is a very complicated dance of relationships with subs. and suppliers. Once you have cemented those relationships, you will have a relatively smooth journey as you continue to build. Starting the whole thing can be a real bitch. There is very little portability in the process. As a builder from the northeast, I wouldn't show up in CA. or CO. to announce that I'm the next big thing. Nor would I expect to make a profit for a year or two after relocating. Every location is a whole new planet, in some respects. New codes, techniques, cost structure, market and marketing, subcontractors and all the issues they bring to the table, etc...... all of these factors require time to explore and develop a knowledge base so that you can run a smooth, profitable company for the long hall.
I could be wrong, but my overall gut feeling is that when it comes to both owner-builders and folks who decide to "dabble" in spec. building, the majority do not do well. They may succeed at a great cost to themselves, emotionally or financially, or they may flat out fail, but IMHO, the majority of them walk away saying "never again". A great example of this was a few years into the recession. My local rural municipality found 135 new homes under construction, that had failed to request an inspection for over a year. They started to contact owners of record to determine what the situation was. The majority of the homes were owned by folks who were building spec. homes as a sideline and got in over their heads. I like to call it HGTV syndrome. "It's easy, and there is a ton of money to be made. I saw it on TV" Not that applies to the OP, given your background, but it's a real common and expensive delusion for many.
The one thing that tripped a lot of these folks up was the subs. The same sub that shows up at my job, with a day's notice and charges X, will end up asking for 50% down, place the new spec. builder at the bottom of his priority list, and charge 150% of the going rate for the same work. It' all fair and done for a reason, but it takes time, paying bills promptly and developing a good rep. before you get past those issues. You are doing the right thing by learning before you leap. That said, generally, unless you are a sharp, aggressive, workaholic, in a hot market, I would pass.