Actually, no need to wait.

Think about it. When you start the car, the engine rpm is way above 1k. If you drive at this rpm, your speed is not really that slow. Even 30 years ago many article already mentioned that it is safe to drive immediately after you started the engine.

my house is about 120m to the main road. By the time I reversed the car and enter the the main road the engine cold indicator is already off and during this time, the rpm is below 2k. Many article said that keep the rpm below 2k while driving in cold engine which roughly translate into below 60km/h at low gear.