There are numerous discussions on this board about WDI inspection certification here in PA. DO a search and you will probably find a dozen threads related to them. Anyone in PA can do a WDI inspection according to the Dept. of Agriculture, however the PAR and most lenders will not accept an NPMA 33 form without a valid applicator ID and business license number in the appropriate boxes. SO, even though you aren’t required to have a license, most of us who perform WDI inspections have gone the extra step in order to become licensed pesticide applicators with a catagory 12 (WDI) endorsement. It is going to cost you a little more on your insurance, but the revenue from offering the inspections yourself should offset the costs in no time.
As far as radon, Pennsylvania has a very stingent requirement to become a certified radon measurement technician. The process can be downloaded in the recent version of the state radon certification handbook.
Neither ancillary service are cheap investments to add to your company, but the revenue they generate is quickly regained if you market your services effectively.