Ask for other published support materials such as worksheets, vocabulary lists, games and extensions based on the series etc. Most publishers have a wealth of support material at hand only to give away. Getting funding In the initial stages you will need a large amount to get enough books to start off. Bulk-buying is cheaper. Some teachers ask each student to buy one book they like and then share them.
Some teachers use their research budget if they are lucky enough to have one.
You will need a constant source of funds for replacing lost and damaged books, updating and improving the stock and so on. To do this effectively needs a lot of forethought and planning specific to your location. Some schools and colleges are lucky enough to have their library keep the books. This is the best option if available because the library will know which books are missing. If there are 200 learners each changing a book every week and each book takes 2 minutes to check-in, check out and restock that's a full day's work for someone.