6 lines are a complicated purchase, the link to our search results page for the exact phones you want is below - all of the available plans associated with each of the 6 lines and payment types are included:
Click here to Compare 6 Line Family Share Plans plus Phones
Also, there are a lot of buy one get one offers currently - you need 6 lines which means if you purchased 3 phones you would get 3 free phones free (as long as you sign up to the carrier financing or monthly payment plans).
You would need to start a new service with one of the carriers that offer the buy one get one deal.
Correct as of: April 2016
AT&T- Buy One Samsung Galaxy S6/S6 Edge/S6 edge+/S6 Active/ Note 5 and Get One Samsung Galaxy S6/S6 Edge 32GB Free OR Buy One iPhone 6s/6s Plus and Get an iPhone 6s 16GB free
Sprint- Two GS7/S7 edge for the price of one + Galaxy Forever on 24-month lease with upgrade after 12 months. Also, $238 trade-in credit with iPhone 6s lease and trade-in of eligible smartphone
Verizon-$100 off the iPhone 6 Plus 16GB in gold with monthly device payments.
These deals may lower your monthly cost from what you see in the link up above.