All the ladders I own except for 2 were bought at pawn shops, you can't beat the prices there.
As long as they are not structurally damaged, cracked, broken, twisted, etc.... then they are good to go.
I got (4) 8' step ladders for $30 to $40.00 each.
I got a 12 step ladder for $100.00.
I got a 24' fiberglass extension ladder for $100.00.
I got a 24' aluminum extension ladder for $100.00.
I got a 24' multi-folding type ladder for $25.00.
The other few I have I bought brand new because there were not any of those kind at the pawn shops at the time.