What to buy?

I'm making pretty good money driving a water truck currently locally out of Oregon, And I found out that The contract that I'm working under is going to be closed. 2029 and I want to start up my own contract with truck setup during that time. I'm currently trying to look for class 8 semis with condo cabs that are cheap and reliable. I have been looking at freightliners, Peterbilt's, And kenworths. I'm trying to find something used that I could get my hands on within the range of 10K to 16k, higher mileage and hours is fine with me I'm just trying to look for something to A metal tank or plastic tank onto the back of the truck, what are some models of truck you guys would recommend with a good engine