I work closely with tech startups and am often asked to help market a seemingly very minimal MVP. More often than not, these startups have no funding and limited resources to market their product. They turn to us for help. I question whether they are even ready to go to market and what they can do on their own dime to make it worthwhile.
I would hope startups in accelerators already have tested their theories....how can you possibly help/mentor someone when they don't even have their own concept down?! If your gut says they aren't ready for marketing tell them that followed by a list of no more than 10 things that they need to achieve before you help market them. Guaranteed that if there idea is a winner they'll blow thru them and it will be a different convo.