The difficulty is really getting your first bunch customers. After that things start to pick up really.
If you are attracting the right customers (not $1/m nulled software customers) they can become a huge factor in terms of growth. Reviews and recommending friends really does go a long way.
With the revenue from those customers and their referrals, you may be able to look into other avenues (I'd recommend staying away from PPC at this stage) but things such as an affiliate program. This truly goes a long way. Overtime you can scale this, we're dealing with millions in affiliate commissions annually.
Overtime you'll have a very nice little business where you have the cash reserves to experiment in other areas -- PPC, SEO etc.