Our staged beds are empty boxes with air mattresses on top, so he would have been in for a surprise when he tried to jump on in!  

I would suggest posing as a renter and collecting applications from similar available properties to see what you have in yours that comes across as unreasonable.I would also move the mattress into a bedroom.

My tip for staging a bedroom: Buy blowup mattresses and put them on totes.

Should I go and buy queen beds to replace my kids beds (what if I go with nice air mattress or a twin bed)?

Obviously sheets and towels but do they also wash all mattress protectors and pillow protectors and quilts each time? 

If so, the investor would be better off buying forever stamps and hoarding them under their mattress for 30 year hoping people still mail in the future.

It's OK for mom and pop to hide their money under their mattress or in their rental property but it is sacrilegious for investors to do it.

The lending situation is improving.But if you're saying you get paid in cash, pay your bills in cash, stuff cash under your mattress and don't pay taxes, you have a different problem. 

I know about the air mattress trick that will look like a bed for the bedrooms, but are there any similar tricks for living rooms?

Larry Loftis on duplex, triplex and quads (see book of that title) runs the numbers and scenarios well..In short, that ugly duckling quad block may have some swans on it if you put on your landlord shaded glasses, the ones that see past the mattresses mayhem out front and that look at cash flow, economy of scale, ease of management, great financing (for four unit or less), cost per unit, etc.....