He can’t afford an iMac plus a TB enclosure to attach a Blackmagic card, he already mentioned that; he, as myself, lives in a developing country where products “Designed in California Manufactured in China” are priced as luxury goods, which they are, based on local sales volume.
Based on just basic affordability, I ran FCP for the last four years on the “under-spec, old system” (Hackintoshed). Any stability issues I ran into were solely due to the decrepit FCP codebase.
In the end he’ll buy the system he can afford. No need to get excited if you’re not a fanboi. I provided him with a datapoint, that even old and relatively generic PC hardware is adequate for Avid.