By all means possible talk to the "last guy". Then take what he says with a grain of salt. Both the employer and employee will have very different perspective

By all means possible talk to the "last guy". Then take what he says with a grain of salt. Both the employer and employee will have very different perspectives about the split. You are the sole judge as to whether it's a warning sign. Personally, I think that the danger sign are the words "Non-Profit" which in turn means "No Money" which is what you pretty much learnt in the interview. In my experience, unless you can routinely "Turn water into wine" you are going to struggle getting funding for anything and don't expect to get paid on time either. Cashflow or rather its absence makes for "challenges". Putting aside all the technical and financial considerations, do you passionately believe in the goals and mission statement of this organization? Only if your passion is total would I recommend taking the job, anything less and you'll be looking for an exit strategy within the year if not sooner.