For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
I do Macbook and iMac. iMacs are always a PITA cause GPUs are hard to find and they are big and heavy, so I prefer to work on MacBooks. 13" Air is my favorite.
1) HDD replacement(good easy money)
2) GPU issues that you'll never/rarely find a good GPU for(avoid)
3) DIY HDD replacement that went wrong meaning ripped LCD connector(good easy money but pry more $$ out of customer for their fuckup and additional work)
Do 1 and 3, avoid 2. Also avoid miserable open ended problems on them. You won't see liquid damage on an iMac unless someone uses it on the beach.. so less common.