building permit, license of construction company, agreement to remove it at their cost when that tenant vacates the property. before,, during and after photos, and an agreement that they will maintain the ramp.
Not knowing the specific laws in PA, if it is a reasonable request you must let them build the ramp to avoid violating Fair Housing Laws. Disability is a protected class. However, the tenant must pay for the ramp, and must return the property to its original condition when they leave. Make sure you document all of this with pictures, etc.
Thank you both. This is exactly what I was looking for.