As you will know, and as this lady's Son will know, any tenancy agreement or mortgage agreement relies on the occupier of the property paying the required rent/mortgage. That's the deal.
Realistically he could try and negotiate a reduced payment if he's hit a bad patch, or try to sort it out in some other way with
his landlord/landlady.
But realistically, if the landlord applies for repossession for non payment of rent, Yes, sadly, it can lead to eviction. Unfortunately too, although a local council might help with emergency accommodation, they are unlikely to be sympathetic where arrears are concerned, unless it's due to sudden redundancy, loss of a partner who was contributing to the rent,or something similar.
A Court order for eviction will give a date by which the property must be vacated, and if ignored will lead to bailiffs ettc.
I hope he gets sorted out. Having been made redundant 3 times it's gut wrenching when your income is suddenly cut off.
Good luck.