Wait on potential funding or move on?

[Elli_056]

My undergrad thesis supervisor wants to bring me back as a PhD student (i went elsewhere for my msc). He's still waiting to hear if he is receiving funding or not which influenced whether he can bring me on again or not (but tells me I'm the only student arranged for this project and funding). However there still is a potential that he doesn't get funding (find out in july). 

I've found other professors with funding that are interested in me this week. Should I just wait to find out about funding from my old supervisor first but then risk the new potential supervisors finding other students? Is it appropriate to explain this to the new ones? What's my best plan of action?

[rising_star]

How long are the other professors willing to wait to hear back from you? Is their funding guaranteed? Are these folks at the same institution or different ones?