How much to drive just to make some extra cash?

Nope. I would look into a temp driver service.

 

Invest $150k or so and do as you please.

Easy - apart from the $150K bit.

 

Depends on what you call part time. If you can go out for a week or two weeks at least a couple times a month then yes you can. Depends on a lot of things but it can be done.

 

We have a couple part timers that do just what the OP asks about.

In the summer when we get busy, those part timers are a blessing to have around. They'll usually come in and work a short day, usually around 6-7 hours. But it's their choice how hard they wanna work

 

The temp service is best. You can pick your hours, and who you work for. One doesn’t fit, try another. Take it or leave it. Minimal stress involved. Some of them pay amazingly well.

 

The temp outfit is a good plan but a lot of times they're looking for a driver with experience. They need somebody that can just take a brief time to familiarize themselves with the paperwork and then blast off.
If there's any agricultural work in the area I'd check into that. During harvest they'll throw anything with a pulse and a CDL behind the wheel. It's a little rough but if you survive it's good experience.
Smaller companies might be a good bet. Larger companies usually have their staffing figured out and don't need part timers or if they have them they fill the positions from retirees. Smaller companies are usually a little disorganized and a guy might luck into something.

 

Look into getting a quad(or maybe tri) axle dump truck, and work local. A lot of companies hire independent owners of short contract jobs. A week or so on this project over there, then a few days over here, etc. One project may need 10 trucks, the other 2-3.

 

Some small companies may consider you for part time replacement to take company units when a driver takes holidays or even emergency/sick leave.
You may consider doing abandoned recoveries for some "local" companies. Fly out or ride as second driver and drive back although cleanup and repair may be required. Offer your services to more than one.

 

If you truly want to be the boss in today's world and economy, it can be done, but there is a lot more to it than just buying a truck. As a former military member
I completely understand what you want to do after 20 years of " Too many Chiefs and not enough Indians".

I have my own authority and work from Dec to Apr pulling a flat. I take the summer/fall off for motorcycle trips, fishing and bow hunting. Everything I own is paid for, so I have no real financial stress when I'm out playing with my toys.

That is, in my opinion, the first step to achieving your goal. If you have a substantial financial burden, the part time aspect is going to be difficult especially with the current rates. Also having paid off equipment is a big part of the equation.
Equipment costs, fuel and insurance costs are very high right now. It will take a pretty hefty cash reserve to get started now.
You didn't mention if you already have a CDL and prior verifiable experience. If not, you are looking at going to an accredited school to get your CDL and more than likely you will have a very hard time obtaining insurance if even possible with no experience.

I'm not going to tell you it can't be done, because it can, but to be the true Boss it's going to take some very careful planning and a rather large output of cash as Blair said.

Good luck on your journey and thank you for your service!