Better you discuss it with CA for registration of company and legal compliance for running it.
To run a lab you need to take various certifications like NABL, ISO etc for trust on your processes of testing facility.
You also need to keep a record of calibration of your own equipment's.
You need to run your lab for atleast 6 month before applying for NABL Accreditation, they will accredit your lab if they found the testing is done in systematic way as per the norms set by them.
So practically you can start running a third party lab by registering a company, the only problem you may face is the trust by the other (specifically if you are trying to get a big clients which are doing big projects as they need double assurance for safety).
