Is it safe to walk to Granville station early in the morning (7am)?

I walk every week day to the train station and back and to me it is pretty safe

I feel safer walking down the streets of Granville than Surry Hills and Redfern.

I'm within 1.5KM from the station and have on regular occasions walked to the station in the mornings around 7-8am and back home after work around 7pm without any drama whatsoever. In fact I've walked home one time at 1am with no issues. However naturally, one should always exercise caution when walking alone late in the nights anywhere, especially so for women. In terms of traffic this depends I guess on the street you are traveling eg. Clyde St gets a steady flow of traffic and so does Blaxcell St and Williams St they're probably the busiest residential streets I believe. I'm male in early 30's with a young family. Hope that helps answer your question and/or concerns. Welcome to the area if this is a decision point for you.

what are they cons of living is Granville?

it is pretty safe if you mind your own business and go or do what your meant to.

It actually is pretty safe.