There is also a chance to have a "trial period" in the sense that you give them a 30 day money-back guarantee. Hence, it will still be a paid trial because they

There is also a chance to have a "trial period" in the sense that you give them a 30 day money-back guarantee. Hence, it will still be a paid trial because they have to pay upfront in order to use it. Or yet another would be to have a fully free trial (no upfront cost) just to get more people to try it out, but then you have to worry about converting those free-trials into paid users, which might not be ideal if you're looking for cash now.