The closest you'll get is buying a certified refurbished one from Apple directly. This way you know FOR SURE that it's unlocked.
(Apple controls whether phones are unlocked via their servers.. so ultimately only they can say if a phone is truly unlocked)
The 7s are not on there yet, but I suspect later this year or early next year we'll start seeing refurbished 7s for sale on the website.
I am interested in a iPhone 6s(32gb) or iPhone 7(32gb) unlocked new. Do these ever have specials or you just pay the Apple retail price pretty much?
If you're going to get an older model, you mind as well get them used and depending on the carrier, you can just buy insurance on the phone by the month. Although Apple products tend to be expensive, they do hold their value more than Android. I think I might just get a Samsung S7 Edge, it was last year's flagship phone and listed for about $800 new, but you can pick up a used one a year later on Ebay for about $275 with a 30-60 day warranty. The same can't be said for Apple.
while i would never say this for ANY other phone manufacturer, refurbished iphones truly can be good as new. Look for manufacturer refurbished models, not reseller refurbished - aftermarket screens function fine, but quality varies greatly - aside from aftermarket lcds not having as good of color rendering, i've seen issues with frame separation from the glass/digitizer along with generally poorer performing oleo-phobic coating (fingerprints).
here's apple's site with their 'good as new' refurb units
the main reason i recommend buying direct is because they replace the battery (or sometimes recertify - you can check the battery cycle count and capacity with various apps and tools) and most importantly, replace the moisture seal around the frame (never gets done with an aftermarket repair). If you buy used, be prepared to replace that battery sooner than later No matter what iphone you buy nowadays, dhon't expect to get more than 18-24 months on the battery before it starts degrading heavily. The old days of "designed for 1000 charge/discharge cycles" are gone - apple now charges their batteries to 4.4V the same as samsung and lg in order to gain capacity at the expense of cycle life.
Otherwise, new iphones are basically (7/7Plus excluded) universal hardware - if a carrier or retailer is having a sale, you may be able to buy the device outright with a discount and unlock. Verizon's iphones are unlocked right out of the gate, AT&T can be unlocked cheap, sprint is prohibitively expensive to unlock iphones (like $120!)
Anyway, if you are looking for an iPhone 7, make sure you read up on the modem and model comatibility issue - The A1660 series iphones with qualcomm modems have far better reception and performance than the a1778 intel variants. The A1660 is available either as an unlocked device or from CDMA carriers (Verizon or Sprint) as the intel modem lacks CDMA radios.