It depends. Costs can range considerably depending on the route you take. You will most certainly need to pay for the costs of any qualifications / certifications and if you are want to be a plumber / heating engineer who is registered on the gas safe register you will have costs there too. The application fee alone for registration on the Gas Safe Register is at March 2020 £190.00 plus VAT taking the total to £228.00 (VAT inclusive) (figures correct as at March 2020). In addition to registering on the Gas Safe Register (presuming you want to work with gas as well as wet plumbing), you will also need to spend money on taking the qualifications and courses themselves. There are two NVQ Level 2 plumbing qualifications to choose from: NVQ Level 2 Diploma in Plumbing and Heating. NVQ Level 2 Diploma in Installing and Maintaining Domestic Heating Systems. There are courses out there which do allow you to fast-track your learning toward plumber qualification, however, there is still a cost with these of course. You should probably estimate between £2000 and £3000 to take qualifications necessary to become a plumber. Of course, you could also go down the route of an apprenticeship which can take much longer.