
Most trades are licensed through a state governmental agency such as a "home improvement commission". You'll need to find the agency in your state and verify that the tradesmen is, in fact, licensed and in good standing.
You want a handyman that can provide a wide range of services. Specialization, in this case, is not the ideal situation. You want to be sure that they can perform a wide range of services.
Working out of a pickup is not indicative of someone who is serious about his business. You want to make sure that you are dealing with someone who is credible and reputable.
You may or may not contact the references (you probably should speak to at least a couple of them), but his willingness to produce the information speaks to his credibility.