Apply for parents GC when they are in the US or outside?

[narendur]

My parents have a valid tourist visa and are planning to visit in March-2016. They've made several visits to the US before.
I've decided to apply for GCs for them. Am I better off, from a time and ease perspective, waiting until they arrive here on the tourist visa and then applying, or just apply right now while they are outside the US?

Thanks

[samlynn]

Gc

The correct way to do it is to file while they are in their home country.

[narendur]

The correct way to do it is to file while they are in their home country.

Thanks. By 'correct way', do you mean it's faster? Is it an easier process? Thanks.