I am always suspicious of statements made by sellers or their agents. If a resort is well run, has good staff, is busy enough to "make money the first day" then why is it for sale?
While it may not the case in your scenario, in my over 30 years in the industry,
I have never seen a business for sale that the owners couldn't wait to get out. In most instances it is just money. They either don't have enough coming in or ... well ... that's it!
Oh ... and as for which training agency to go with ... it has nothing to do with the quality of training. It is all marketing. I know there are a lot of religious zealots that will beat the PADI, SSI, NAUI, etc drums and sing their praises, but you just need a company that will support you for the money you give them. When you list as a resort with one of them, you will be listed in their magazine, given an opportunity to advertise with them and to buy their insurance. I know you are from the online world, but (in the USA at least) the diving world still loves their paper magazines and the best ones come from PADI and SSI. Listing there gets your name in front of your potential customers ... instructors and dive shops.
My advice (and it is worth exactly what you paid for it!
) is to put your business plan together, put your money together and then do your shopping. If you find something you are interested in, go there for a couple of weeks as a client/customer and study the operation. One week isn't enough so the longer you can visit, the more opportunity the staff has to screw up.
Worst case scenario ... you spend a couple of months visiting dive resorts around the globe and keep a big chunk of cash in your pocket. Best case, you find a little gem that just needs polishing.
Good hunting!