Any PC will run FM, just at different speeds. That PC (Intel i5 2400 specifically) will be pretty slow, but the price-performance ratio is decent.
Basically just look at the GHz for FM and add ~10% for each new iteration (instructions-per-cycle improvements). For instance, i5 2400 = 3.2GHz (turbo all core). i5 10700K = 4.7GHz (turbo all core) x 1.7 (7 new iterations since i5 2400) = 7.99 GHz. It'll be a bit off, but it's pretty accurate.
An important exception is the latest AMD CPUs which have a 20% instructions-per-cycle improvement on previous gen, making them a bit better than Intel GHz-for-GHz.
My recommendations:
Budget best bang-for-buck = i5 4670
Medium range = i5 10600K
High end = AMD 5600X
Some advice for anyone buying a new PC today for FM:
You can't rely on the 'turbo' speed because it bounces around a bit lower than the advertised figure, and the stock voltages are set high so for that extra ~200-300Mhz or so you get out of a high end CPU, you're not only paying an extra ~$150 for the CPU itself, you're paying an extra ~$100 for adequate cooling too.
If you avoid the turbo clock and do a manual overclock with a set optimal low voltage, then it brings up other issues - If you don't have ~$150 cooling, you're going to potentially ruin your CPU if you ever use AVX-based programs (i.e. encoding video). All-core overclock generally just can't reach the advertised single-core turbo boost because the voltage required increases exponentially. With an all core overclock, the difference between a 10600K and 10700K on budget cooling is only about 200MHz.