There is nothing to stop you taking advertisements. Local ones are best. You may get some from your local taxi company, butcher, baker and others that may already supply goods or services for your events.
I would caution against any agency that contacts you. There is often little or no control over what is advertised and some are devious enough to show one advert to you that would be acceptable and another to the rest of the world that would not!
Consider using an affiliate scheme. You have full control and receive a commission on any sales made via your website. Please see http://club-sites.co.uk/keyfeaturesexplained.html#earnmoney for an example that Club-Sites can supply even if we don't host your website.