I can only speak for myself. I have been training clients via Skype for many years now. I have clients in Europe and in the US. It has been a great source of revenue for me and the best part of all is that it can be done from anywhere. I do both 1-on-1 and group training. If you have clients who you know they can be motivated to workout with you even when you are not present (except via Skype) then building a business through this type of means is a great way of adding to your monthly revenue.
My clients come either through referrals and/or by placing ads at the targeted market area which I’m looking to attract new clients. I hope this helps.