Condo association wants to deter non-resident owners from buying

We have a 26 unit condo in PA. Five of the units are owned by nonresident owners. The board would like to amend the bylaws to prevent any new investment/rental properties in the building. Do we need an attorney for this? Is it costly? Any suggestions? When parents buy a condo they put it in their son/daughter's name. They cannot serve on a board and it is difficult enough to find people to serve. Will additional units with owners who do not live in the building lower our property value? Thank you for your help.