Now I see why you put in a 12K kitchen -- seems about right for a 150K
house.

It sounds like you're leaving some costs out. You can correct these
assumptions, of course, but let's say one were interested in "flipping"
a house like the one you describe. Costs you didn't mention are
settlement costs -- agent fees to begin with average about 5%, and
that's when you buy it and when you sell it; if we adopt the convention
that you bear half these costs, that's $7500; add other fees and taxes
and you're at least up to $10K between the two transactions. Now let's
assume it took you three months to "flip" the house. You're paying the
mortgage for three months -- that's another $3000, say. So now we've
hit $13,000. What else is missing? What about all the time you put
into the house? You probably put a couple hours a week in, between
shopping for the kitchen, talking to agents, cleaning, painting, and
doing other odd jobs around the house. What about the value of your
time? How much do you make an hour? $20? $30? 13 weeks x 2 hours x
$25 = $650. Prorated property taxes, utilities for three months, etc.
What are we up to? $14K?

Sounds like you made $4K. Not bad, but not the slam-dunk you're
portraying. It's probably true that there are some arbitrage between
the turn-key crowd and the bottom feeder crowd in general. (From the
buyer's side, you can exploit this by buying a fixer-upper.)

Congratulations on your success, but I don't think it's as obvious as
you say that the OP should follow your example.