The user then needs a notebook to read all the data and show on a decent size screen. Of course they need Linux, not the horrible proprietary operating systems from Apple, Google, and Microsoft. The local suppliers will not let me performa test install of LM 19 on their demonstration machines.

What is the lowest cost notebook with Wifi, a replaceable disk, and can run Linux Mint 19 without modification?
I used a netbook for a while. It had Wifi. I upgraded the disk. Most cheap devices have soldered in storage that is too small or they use an unrelable rotating disks. I usually recomment an upgrade to an SSD of at least 256 GB. eMMC storage is not an option.
I also found the netbook 10" screen too small for normal use. At that size, you might as well look at photographs on your telephone. I currently 14" and most of my friends have 15".
My processor runs Cinnamon at a reasonable speed. I have not tested modern processors. I did test a previous MATE and found it about the same speed as Cinnamon. LXDE was measurably lighter at the time, against LM 18 Cinnamon, but I had problems configuring LXDE. I have not tested anything else. What would be the minimum speed low power processor for LM 19?
Our local relaible retailer of laptops has a Celeron N3350 based laptop sitting at the lowest price for a 14" screen. Unfortunately it is locked into eMMC storage.
For slightly more, I can get a 14" laptop with an AMD A4-9120 and real disk storage. This is the machine I would probably recommend as a starting point if LM 19 would install direct and work at full speed.