Personally I wouldn't worry too much. I've sold plants at school fairs for the
last two years and raised a couple of hundred pounds each time. Things go from
50p to several pounds if the plant justifies the price, eg. a young sapling of
Betula pendula or a largish Fushia in good condition. If something is in
flower it does go for more.

Plants are generally free from breeders rights unless they are very new. Most
plants can be propagated and sold with impunity. My mother donated hundreds of
African Violets for sale when I was at school. None had any
rights/restrictions placed on their propagation or sale. I think breeders
rights are a relatively new thing. I actually have a bit of a problem with
them, though I can understand some breeders wanting to ensure they get a fair
return for any investment they have put in to breeding a new variety of plant.

In general, I wouldn't worry. Hope you have great success.

Dave.