Hi and welcome,
for me it was a case of doing lots and lots of research via professional magazines and the internet.Set up costs can vary hugely from company to company and sadly this can sway you into whatever decision you make because unfortunately we aren't all loaded, so cant take on whatever brand we want regardless of repuation etc.(some of these product lines cost thousands to set up,some wont let you be mobile,whilst using their products,some require you to have more than one treatment room in your salon)It's not easy
Emailing or calling various companies and asking for samples is a good idea as well as going to various salons for treatments and seeing what you personally like.
Be prepared to do an awful lot of groundwork,make sure that not too many salons in your area will be usng the same product line as you or this can make things difficult with enticing new clients,i.e price wars and ill feeling.
Also sometimes it takes several contacts from you to even get a sample sent to you,it can feel like your interests are not appreciated at all as I and many others have found out,remember if they can be like this with you as a potential new client what will they be like after?(customer service,help etc)
Anyway,hope some of this helps.There are many wonderful facial product lines out there,some aren't very well known but are just as good,dont rush into anything,it's probably one of the most important decisions you will make for any beauty business and the most expensive,other than equipment.
Good luck and happy hunting:hug: