I have set up a DNS server in my home, will I have to wait for the isp to refresh there cache before DNS is active?
Some website I have found says this is called "DNS propagation time" and how long could this take?
This is dependent on whether your DNS server is actually taking over any actual DNS configuration for your Internet Domain - e.g. NS entry/function. If your DNS server is just a free-standing internal server and no actual Internet DNS entries/updates are required, then no impact.
If is it taking the place of or being placed in as an additional NS for an active Internet DNS domain configuration, then it will require some time for the entry from where the actual Internet DNS server was made to propagate/update to the rest of the Internet DNS servers. This used to take around 72 hours in the past, but may now be as quick as completing within 24 hours.
There's a lot of nonsense that people believe when they talk of "DNS propagation", that is based upon a wholly incorrect mental model of how the DNS operates.