Making offers with no testimonials or evidence of success

I got all excited to make offers until I imagined myself on the phone with someone or even just emailing them and what if they ask me about client testimonials, i.e. proof that my system works? The only proof I have is the work I’ve done with myself and those results.

Do people generally want this information when an offer is made? Or do they just believe you and say ‘yes’ or ‘no’?

If they do ask for that, what’s a professional answer?

Thanks in advance!