I'm pretty detail-oriented and feel like I could do a good job at plastering patches or even skim coating a wall.

If it is possible spend the extra pennies most good doors last a long time .

However I was thinking, if I focus more on homes without need of extensive rehab - like only needs a fresh coat of paint, minor bathroom work, I can manage it myself over a weekend or a regular work week. 

We spend 10s of thousands on software and its worth every penny.  4.

Very few plumbers here in Chicago enjoy repairing old plumbing as the materials are not as easy to work with as the newer materials they learn to use (pvc, pex, copper, etc). 

Classic flip job with laminate floors, new coat of grey paint, etc. 

Of course, he/she has to pay tax on every penny he/she receives as interest.

But we have not have had to pay a single penny of our own money on that home for at least the last 7 years.

If a Seller tells me he had his polybuytlene piping replaced and it is now all PEX/copper, I am not going to rip into the drywall to verify.

Cars that drive kick up dust and would coat one unit while the other could go months without a change.