Advertising for businesses and companies

I want to put up some advertising boards in my town and get shops and companies to advetise on and charge them. Is this permissible?

Secondly, I wont get companies that are dealing in haraam to advertise with them, so it will probably be businesses like supermarkets and hardware stores etc. But my problem is that am I allowed to advertise for them if a part of their business might be haraam or doubtful. For example I personally dont eat commercial chickens even though it might have a halaal stamp on it. I prefer to stay away since I feel it is still doubtful, will I be able to still advertise for that supermarket that sells it. Or if there is a car dealer who sells cars but organises a loan for a customer based on interest then am I allowed to advertise for him.

Also is there any guidelines that you can give me and advise?