Read entire post looks like OP decided for singles not tandems but regardless of what you choose I suggest getting 2nd hand or used.
New boats can run you up to $1,000 or more each. Second hand they drop in price, as much as 30-40% or more. The reason this is important is because if either you decide paddling is not for you and you want to get rid of them, or that you wish to upgrade and trade them in, as long as the boats are close in material condition to when you bought them and not damaged you get back more or less what you paid risking you little to nothing.
This goes 2x with SOT because they are the most beginner boat, the most popular boat, and many people buy them thinking they will like them. Many love their SOT’s and swear by them keeping them forever. Many don’t and think they’re too heavy and give up or want an upgrade. Since the SOT’s are the biggest seller by the numbers, this means the 2nd hand market out there will benefit the used buyer with selection and pricing to match. It also means your boat will be very easy to sell as well if you don’t like it or want to eventually trade in.
The classified ads of this website are pretty good. Craigslist also works. Just plug in your zip code and see what you find. You can try local pro shops as well, many post their 2nd hand offerings online or you can call them and see what they have to sell. Many pro shops also have season end or year end sales but usually this is in the Sept/Oct time frame. They will sell off their rentals and boats they use for lessons and SOT’s are popular for this end. You usually get better deals this way than consignments but not always. It pays to be patient.