[bluGill]

Maybe, maybe not. It really depends on many variables that are different for everybody.

If you work (or have worked) in construction you have the experience to do it at less cost. If you have friends who will all share labor to build their own houses, then you quickly get the experience.

If you can't earn more money in your spare time (burn out from working too many hours at your "day job" is very real!) then your labor is worth zero and you save money. Even if you could earn more elsewhere, if you enjoy working in construction once in a while your time is less valuable.

There might be market distortions that mean labor for construction gets paid more then the real value. Thus making you more competitive.

You might have a job that is less valuable than construction, and thus your time building your own things is worth less than the person you might hire.

You might have reasons (valid or invalid) to believe the professionals would do a bad job.

You might be a complete klutz that should never touch a tool. You might hate building things. You might be disabled. You might want to do something else with your time. All of these are valid reasons not do something.