Or, learn how to work with agar, and then you won't care if there is some initial contamination in the spores since it is easy enough to separate out on agar.
Working with agar can be cheaper than constructing a flow hood, and work almost as well.
When I purchase liquid cultures of edible mushrooms I find it is not too unusual for them to have contamination. Therefore, I usually start on agar. Makes the cultures go a lot further as well. I don't have a flow hood but I get less than 10% contamination just by spraying with lysol and cleaning my instruments with rubbing alcohol (I never use a flame either since I'm always afraid of starting the alcohol or lysol vapors on fire).
If you do take spore prints, keep in mind that they have to be used fairly quickly, especially if not stored under optimal conditions. I had dozens of spore prints of cubes, and while they worked fine originally, after 4 years not a single one was viable anymore. I had stored them at room temperature in a drawer. So one has to grow out the mushrooms and take new prints at least every couple years in order to have a perpetual supply independent of vendors. And I try to order questionable (legal but possibly watched) things from vendors as infrequently as possible.
elphologist