To create a campaign all you need is to pay for the Ethereum gas for registering and deploying the campaign on the Ethereum blockchain. Typically, that cost between a few cents a single-digit US$ amount.

When running a PPC campaign, you need to lock in the amount of the rewards to ensure that referrers will have access to the rewards they earned.
All unspent locked amount is returned to your wallet when the campaign is ended.
In case your locked amount is consumed before the target end-date of your campaign, you have the possibility to top up the campaign locked reserve to ensure it continues until your selected end date.

When the rewards for your campaign are set up as a percentage of the amount collected in case of conversion, no locked fund is necessary, since the reward is automatically deducted from buyers or donators’ payment as defined by you when you created the campaign.

Some campaigns are run with no rewards, in which case, the only cost is the gas fee.

In any case, rewards are always linked with a successful action, so you risk nothing.