Build Assuming a Paying Customer

I've been working on turning a site I built a while back into a site I could charge for. When I built it, I assumed that:

1. I was building it only for myself.
2. If I ever wanted to open it up to other folks I wouldn't want to charge for it because it'd obligate me to maintain it... So I'd monetize by advertising, associates programs, etc.
   

Realistically you have little chance of building something that will generate enough traffic to make money off of advertising so stop fooling yourself. On the other hand if you build something useful (and if it's not useful then why the heck are you building it) you can probably charge for it... Maybe not a lot, but $5/mo or something, and 1000 people paying you $5/mo is nothing to quibble over.

So don't be dumb like me because when you do to turn it into a pay service you'll discover all sorts of work that you didn't do the first time. Such as

1. Documentation and help sections
2. Authentication/security needs
3. Permissioning and roles
4. Missing editing functionality that you always figured you'd just do by hand
5. Scaling problems that you were ignoring because it'd only ever be for a handful of users
6. Ugly UI that you tolerated because no one really cared