What are you out to them about already?
If they already know you're gay and that you're not monogamous, the idea of money being involved can be rather less of a shock than if it all comes at once.
If you are out to them, I'd bet the phrase 'being careful' (meaning don't get HIV or murdered) has been used by them, so you could demonstrate how you are, in fact, being more careful than half the men on the scene.