Absolutely it is sleazy to predatory, along with most offers to 'mentor'. 99% of training 'offers' are indeed code for no strings attached fun. Be wary of strangers offering to do you a 'favor' as there still aren't any free lunches. Unless someone is offering to teach an actual skill then you aren't getting trained in anything but being a patsy.

On the flip side, I certainly have trained submissives in real skills before. However, these were all non-sexual in nature and skills which were needed for day to day living, such as how to write proper business correspondence or how to create and stick to a budget.