car finance question

Hi All

I am looking to purchase a 3 year old 5 door Diesel hatch at some point in the future on finance, I seem to recall if you had a 4 year deal, on month 25, or after a certain period of time, you could return the vehicle with nothing more to pay. The idea was that should the equity in the vehicle be greater than the balance on finance, this would be the deposit on the next car.
If you can remember the Lada/Yugo deals in the 80/90’s I’m sure this is how they worked.

I cover around 17 – 20k per annum, so a PCP deal could be out of the question, so can you still do this with the finance companies?

Thanks