Is it normal to ask for rental agreements?

[William Craft]

I am currently in talks with a seller of a property that claims he is getting $2,000 a month in gross rent, but the average in the area is about $1,500. I asked him to send me the rental agreement to confirm before going to look at the property with him. Is that rude or inappropriate? He said he doesn’t want to share that information until he knows me better / knows I’m a more interested, but I can’t confirm I am interested without validating the gross rent.