I have an established salon in Doncaster (not far away!) and I think looking back, I wish i'd gone into lashes & gel earlier! Whatever you do, pick fantastic reputable companies that have a great name. Cliens are very knowledgable lately, and know what to ask for. Get your basics in first, mani, pedi, facials, tinting, gel, acrylic, build up your client base and then start pumping your money into the new stuff!
As for cheap to buy...... you really do get what you pay for, sorry hun, but as I said before, clients tend to know the big names, and will go to salons with a recognisable, well known brand in their windows.
What do you do currently treatment wise?
how far on are you?
are you confident in your treatments, do you excell at something, have a natural flare etc that you can channel your energy into and make it your selling point to get going on?
These are some things you need to think about loads, that is where you will get your edge from, careful thought and planning, and the BEST not the CHEAPEST training, tools, and products.
I'm not saying blow your budget and skint yourself, but start as you mean to go on. If you build your rep on good basics, the rest will follow. You need that edge being above a hairdressers especially as you really have no shop frontage.
Nail them down to advertising space, price lists, window posters etc.
Check that their receptionist can take your bookings for you, make sure that she/he knows your pricing and treatments so they can cross sell for you.
One last thought, is there a client base there already? Was it an existing beauty room? If so, try and find out the popular treatments from the girls downstairs.
hth and good luck x x