"No ads" is a good alternative, because the extra spreadability you get is worth far more than the pennies you'll be able to extract from advertising at an audience of tens or hundreds.

The other alternative -- and again, "no ads" is better, is to put up your add blocks, seed with one ad for a related affiliate offer or even an ad-looking block towards a page in the space, and then have the other blocks say "Click here to buy this space." You can then do the simplest possible thing to enable that -- e.g. email me and I'll take your payment by Paypal.