Cash basis:
Cash in hand, recognized. Cash out, recognized.
Keeps it simple :)
It is simple. I offer a 30 day money back guarantee. But if you cannot commit to credit card on day 1 knowing that you have nothing to lose, then you are not the customer I want.
Research cloud services, compare prices, at the "cheap level", you can swap Digital Ocean for Vultr, OVH or even others (http://www.hostingadvice.com/reviews/vps/)
Throw more technology at it, find a PaaS that can rack docker instances (Flynn is my preferred one) and mount local versions of your expensive cloud services (Redis vs ElastiCache), (MariaDB vs Aurora), (Riak-docker vs S3). Every penny you save in your "infrastructure" setup can be put towards keeping the lights on.
You can run a company that makes $5,000 a month on $20 worth of Digital Ocean droplets (it's sketchy, but it can be done)