You don't need huge amounts of space to retail, you don;t even need the ability to sell. Just have faith in the products and never sell something the client doesn't need.
When I start a client on facials I tell her that for the first treatment I will talk her through it so she understands what is happening and that at the end I will show her the products I recommend to use at home. I say it's up to them if they want to take any, no pressure, but just so that they can see what I advise to get the best results as quickly as possible. It's very rare that a client doesn't buy something, even if it's jsut a cleanser and moisturiser.
When I do a full set I now just tell people that they have to buy a solar oil, and usually they do. If they don't want to then they tend to say they have one already, but even then usually buy one at the next appointment.
The one tip I will give is if you are serious about your business and serious about retailing then get a credit card facility. I had one in my home salon in the UK and my retail sales were really good. It really does make a big difference. Shop around though as you can often beat banks down for the best rate. I couldn't believe when I read in PB that one company is charging 5% commission, that's outrageous. You may pay a little more for one in a home salon, but nothing like that amount!