If it is a rescue you would want to know:
Past medical history.
Temprement of the rabbit and what type of home they think it would be suitable for.
What food it is on, although good rescues will give you enough food to transfer rabbits over to a new food.
Is it a good hay eater. Poor hay eaters are at greater risk of dental problems.
Have a look at the size of its poo. The bigger the poo the higher their intake of fibre and the healthier their gut will be.
Is it castrated or speyed.
Vaccination status and when they are next due.
Will the rescue assist you with bonding two rabbits together, this is very helpful if you are not experienced at this.
Now the weather is improving the issues surrounding outdoor and indoor rabbits is minimised. In the colder months this is important.
I am unable to advise about getting from a breeder as I have never considered this an option.