Allocate properties to homeless people & maintain tenancies

We are Fresh Start Housing, a small, independent charity that houses homeless people (usually street-homeless) in private rented accommodation. We have just over 100 properties whose landlords allow us to select the tenants and therefore we have just over 100 tenancies. We also have a hundred or so applicants who have registered with us and are waiting to be housed. We need a computer system to replace our spread sheets and manual files. We register people and we register new properties. When a property becomes vacant (or we get a new property) we invite a few people from the waiting list (registrants) to a viewing. We allocate one of them to the property and then they become tenants. There follows a lot of paperwork we do using MS Word. Tenants pay rent direct to the landlords, so we have no accounting problems. We maintain a link to the tenant for ever, particularly in the first month or so while Housing Benefit is sorted out and the flat's teeting problems are solved. We need a system for logging calls from our tenants and the calls (and other actions) we make because of those calls. This is above and beyond the system described on the attached document. We expect the underlying database to be SQL compliant so tht we can use a report writer and any later package we obtain can share tables on the existing database. We want to own the source code of any tailor-made solution. See the attachments for details.