I would go without hesitation for a Dell Latitude.
I loved the E6510 (15.6'') / E6410 (14.1''). They're robust, a dream for maintenance, and are easy to clean. Both support 8GB DDR3 (confirmed), maybe 16GB.
Previous E6500 (15.4'') / E6400 (14.1'') series are similar for maintenance.
Those Core 2 Duo are still performing very well with Vista with only 4GB DDR2 (or even 2GB !), if coming with a dedicated graphic chip (Nvidia NVS 160M) and a professional grade SSD. (Word or Excel opening in less than 1 second on Windows Vista.)
They are probably a little aging for Windows 10. I haven't attepmpted this.
E6500 / E6400 had the issue of peeling speakers paint.
More recent series, with the E6520/E6420 and E6530/E6430 design, are also very good, although maintenance is a little less easy, as having more than one screw on the bottom to open them. The E6530/E6430 brought USB 3.0, altough E6510/E6410 series allows adding a USB 3.0 socket though the use of an ExpressCard and have an eSATA socket as well.
Later series (e.g. E6540) are less reparable, at least for the display panel assembly which is monolithic. (The LCD panel is sealed.)
If the notebook stays at work or home most of the time, I would go with a 15''.
In your case, I would pick the E6510 (easier to clean) or the E6530 (more recent).
Newbies focus too much on the RAM amount. I would'nt.
A dedicated graphic chip (NVIDIA), the processor and an SSD instead of an HDD are way more important.
For instance, I have some old E6500 with Core 2 Duo, NVIDIA 160M graphics and 4 GB RAM that still beat more recent E6520 with i5 but standard Intel GMA graphics. Both have a good SSD.
The question is always where the bottleneck is. It is useless to have tons of RAM if the processor cannot follow or if the HDD is slow. Nowadays it is rare going out of RAM with standard desktop use. 4GB often suffice and 6GB is comfortable.