Not so long ago it was quite the big new idea to acquire as many cheap properties as possible by way of the buy to let mortgage schemes. There were tales of young entrepreneurs amassing as many as 30 apartments in Liverpool and similar numbers in other cosmopolitan cities. The idea was to do up the first property into reasonable shape for renting, luckily far less effort and expenditure is needed for this rather than to sell on. Then once in safe legal condition, the place is rented out and funds gathered for the next mortgage and so on.
This system of property ownership came a cropper when property prices fell and many were left owning property worth much less than the mortgages being paid out. These days more caution is applied to buying portfolios and professional property management is a good investment to keep the porfolio in good safe and legal condition to attract the higher rental yield.