As an independent consultant, I am trying to advocate linux and open source applications to my customers as much as possible. A new customer is in the business of renting social housing. They are currently poorly organised, with most information kept on paper. This is highly inefficient.
I am trying to setup some kind of organized system to manage the houses they own. But I haven' t find much in the open source scene yet for this kind of task.
Ideally, I am looking for some software that helps them keep track of their houses, their tenants, the repairs, the complaints, and so on. Preferably a client-server solution as they are with 3 to do the work.
Has anybody heard of an open source solution ? Or any suggestions worth further investigation ?

Thank you very much.