Which flight sim for a first timer with modest PC spec

Last year FS2020 caught my eye, and as some who's dipped my toe into the world of real life flying, the idea of getting into a flight sim appeals to me. 

The thing is, having done my research it seems I'd need to spend over £1000 on a new PC just to run FS2020 on it's basic settings and I can't justify spending that on something that might (for me) end up being a short lived novelty.

Therefore I am thinking why not try one of the older sims, that can run on my current PC? My current PC is around 6 years old and has an i5 4400 with 8GB ram and a Quadro 410 graphics card. The GPU is geared toward AutoCAD etc so I expect this would need swapping out to something gaming oriented. But a second hand GPU for, say around £50-£100, is more easily justified, and if I get the bug I could upgrade in the future.

Bearing in mind I have only so far played with the google earth flight sim, can anyone recommend an older flight sim and a cheapish GPU to slot into my current system? My current system below:

i5 4400
8GB ram
108gb SSD
930gb HDD
Quadro 410 GPU (assume replace)
Windows 10

Many thanks