If I can do without the L1 course that would be nice.
That depends on the laws of your country. Some allow everyone to do thermal imaging and in some you need to proof that you have a formal education ...
it is a certificate showing some expertise. That can be helpful in getting an easier entrance to customers and most likely also in charging more for the service.
Not really - I have learned programming from books back in the days but I had never any formal education. Anyway I have worked almost 15 years as a full-time programmer and I have done multiple hundred of projects.
No client ever asked me for some certificate or the like. Now a an professional expert I had to do basically certs for everything to proof some kind of education. If you are going to write expert opinions for a court or you want to do some kind of work for the public authorities then yes - you will need to show at least a L1 training. As far as I know for an expert opinion in court you will need a L2 at least.
So it depends on the country and it depends on the type of work you do. If you want to rate the energy efficency of homes for the approval of state subsidies then you will need a cert. and a better camera also. As far as I know most european countries request at least 320x240 resolution for such reports and for expert opinions.
If you use it as a tool helping you in your work like a plumber would use a cheap thermal camera for tracing heating pipes or an electician would use it to see how the underfloor heating works, then you can do what you want... My GF estimate real estate pricing and she checks most buildings with a thermal camera not for her conclusions but to see if something looks out of the ordenary and in such a case she calls an expert to investigate further.
In case you do some kind of reporting for the client you have to check if thermal imaging is something you can do without a certificate in your country.
And I will PM you on FB, having the possibility to ask some questions to knowledgeable people would be really helpful too.
Looking forward to it. We can discuss that further on FB with some friends of mine which have far more knowledge then me...