Its impossible to say, because we are not the ones tattooing you.
Usually tattoos are priced by the hour.
How much an hour is depends on the shop you go to. In my area, an hour of tattooing costs anywhere from $60 - $150 an hour.
Its difficult to estimate the time frame for this, because we don't know where it is going, and we can't see an image. I would assume that this will take a few hours, anywhere from 2 - 6 depending on the speed of the artist, how many breaks you need, and how detailed everything will be.
You will want to go to a good artist who can hand write the script for you, and who has clean lines. Anybody can do basic florals that look good, so focus on finding someone who can do nice clean lines, and who can do hand drawn script nicely. With a tattoo this large, with a sentence, you want something that flows with your body, not just simple straight lines because that will look really weird.
If you know where you will be when you are wanting to get this done, start looking around. Google different shops, and look them up. See if they have social media, like facebook or instagram. If they do, you can see their work and see reviews on their stuff. Better artists will cost more, but its worth it for something that is permanently on you forever.