Well obliviously you have a plan, so you need good solid advice from one who has been there.
Yes you can find deals for under - $25,000. I would go just a little more then $20k for a few reasons that I won’t talk about here.
What kind of truck depends on a couple things, what company you are planning on being with (or did I miss that) AND how much you really expect your standard of living is going to be like while on the road. It really has to do with opportunity costs in this business.
A few companies will not accept anything older than say 5 years old. They feel that they either have an image to up hold or they don’t think you are capable of maintaining the vehicle properly – both are BS but it is something that you have to live with. I personally don’t see anything wrong with an older truck, to be exact operating costs may be cheaper but again it is a company thing.
Now your standard of living is a completely different thing, either you don’t mind living in a small box or you want to be an RVing style expediter, which if it is the latter, $20k or $25k won’t buy the stripes of one of them quarter million dollar porcelain palaces on wheels. Also I would not expect anything outside of a box with some insulation and well worn interior but again it does not bother a lot of people who make a living out of this stuff. I would not worry about the sleeper except for a place to put a fridge, hang your cloths and so on.
The last thing I want to mention is you are the buyer, don’t be pressured into buying the truck until you have it checked out, especially when you talk about a lower priced truck. Take your time, get a mechanic you can trust to look at it, get the oil analysis, got the ECM dumped and printed out, go to the dealer have them run the VIN and so on.
It is right now a buyers market and you may find something a little bit more in the money area but more equipped.
Oh before I forget, you may pick up one of them trucks with that air cleaner thing outside for cheap, I was offered a tractor a while back for well really cheap and turned it down because I have no place to bring it too or the time to clean it up to sell it. Don’t worry about that air cleaner thing because if you invest $15k into a truck like that, you still can operate cheaply enough because your payments will be nothing and dump the truck if it don't work out.