If your client can afford to meet all costs of buying and moving home it is very unlikely that they will be entitled to a grant towards the purchase. Whilst grants are not always awarded on the basis of a calculation of need (means testing), the general principle that must be met is that the disabled person cannot be suitably housed without the grant.
At present there are two specific grants for purchasing a home - Rural Home Ownership Grant and Special Needs Capital Grant. Some local authorities may help in exceptional circumstances, but whether there is support available for your client will depend upon the area of Scotland they live in.
Your client may, however, be eligible for assistance with adapting their property for the needs of a disabled person or making essential repairs. All local authorities administer this funding, although the sums available and the time taken to receive a grant differ widely between authorities.
Applying for, and using, grants to finance a house purchase or adaptations is rarely simple. Regardless of the type of grant, your client's options and choices regarding their home will be restricted.
