how much money do you think we all have at our disposal to throw at our 20+ year old trucks?
It's not a matter of money, or the age of the vehicle.
It's a matter of "
how committed are you to fixing the vehicle". There's just no point to owning a computer-controlled vehicle that you want to D-I-Y, and NOT having a suitable diagnostic tool.
Far as I'm concerned, you need a compression tester, a vacuum gauge, a fuel-pressure gauge, a 12-volt test light, a spark-tester, and a typical automotive multimeter in addition to the scan tool. If you buy all this at Hazzard Fraught, you'll be unable to trust the results because the tools are so cheaply made. Better to buy "good used" tools than "new junk" tools.
A proper cylinder leakdown tester, and an automotive oscilloscope/graphing multimeter are optional but recommended.
Not everyone can get their hands on a scan tool that easily. Do you have a link for an inexpensive new tool that reads OBD-I?
I have no insight on "new" inexpensive (consumer-grade) scan tools. Frankly, I don't trust 'em.
I bought an ancient Snap-On MTG2500 (similar to the more-popular MT2500.) The MT2500 can be had for $150--$400 (and up) depending on the software cartridge(s) and connectors included. The '2500 series software support ended in 2009. They're WAY out-of-date for professional use--but with the right software, they're good-to-go for 1980 1/2 to 2009 (My unit has software support only to 2006.) As the newest vehicle I own is a 2003, I'm all set.
There are many other manufacturers of professional-grade scan tools, and other (newer) models in the Snap-On line. The '2500 series was replaced with the Solus, which itself has no further software support. The Solus was replaced with...Solus Pro (?), then Solus Ultra, and the current model is Solus Edge. As the tools get newer, they get more expensive.
Software-and-a-connector-cable for use with an ordinary laptop computer is probably a less-expensive process for "new" product. I've got no experience there.