It all depends on what you are calling start-up costs.

If all you mean is reseller hosting space and some money in your Domain reseller account, then easily under $1000.

As an example;

You want to pre-pay 1 years reseller hosting after you investigate the companies out there and know what to look for.
At least 1GB and 10GB (10 to 1 works well for me) and features. $100-500.

Money in your Domain Registration account $200 or so to start with. Again shop around and don't go the Enom or Wild West routes. I pay $6.75 per domain with no deposit or minimum and I only charge my resellers $8.75. I keep money in my account because everything is automated and I want the registrations to start as soon as they press enter on the PayPal button....:D

Billing/automation software $35-150, or use the free one in new versions of Fantastico.

That's about it for out of pocket costs, the rest is just your hard work and 2-3 years of waiting to make minimum wage.

Michael Kelly
Rabbit Web Hosting