You can join the WQA and get quite a lot of education without going through certification. Depending on how much business you do, the cost can be quite high IMO. At least it was when I was a member 20 years ago.
Again, in my opinion, I see certification as a marketing tool aimed at those prospective customers that lean heavily toward warm'n fuzzy and don't do any research. Some of the largest crooks in this industry are WQA members and have their sales people Certified.
Are you going to be in a rural or urban area? If small town rural with individual wells, certification is probably not very important, you really must have someone to guide you or have all the 'education' you can muster or you will not survive long enough to develop sufficient experience to see you through the start up period (1st 5 years). And if you get a bad word of mouth reputation, certified or not, you'll be gone much sooner.
In an urban and large suburban areas... IMO that's where the biggest crooks flourish because the population seems to depend on things like certification and the crooks hone their abilities to be able to find a new sucker around the next corner.