I am meeting with a retail chain who want to sell my paintings in shops and online...anything I need to know?

They have 20 baby stores over the UK and my illustrations are for nurseries. I am just starting out and know very little of retail. I guess they will print them and sell them and I'll get the royalties but I could be wrong. I wont sign anything obviously but dont want then to take advantage...a little bit of an income would be great even if very little...not sure what percentage to take etc. Any info would be FAB! xxx