Many shops in medieval times were built roughly along the same pattern. They had a large front door and either one or two unglazed openings at the front. If instead of walking into the shop you walked down the long passage you usually came to a hall. This would often have had an open fire and a large table with some stools, maybe a cupboard or two and some other bits of simple wooden furniture.  

There would have been either a stair way or a ladder up to a bedroom. This, room would have had unglazed windows with shutters and sometimes there was an upper continuation of the hallway.

Many people were too poor to have candles and for many they were a comparative luxury. There were no paraffin wax candles which most of ours are, they were made of beeswax or tallow, a type of animal fat. Frequently people used spills instead because they were cheaper. Often if you have a fire you might not use even them. The firelight would frequently light the room sufficiently as most people did not need to be able to see well enough to read, although it was common for women to sew in poor light.