Both in terms of law and airbnb policies. Can your account be closed f. ex, because you, as a host accepted cash (and for additional circumstance - also asked for it yourself).
Also what about partly cash? Like if I am asked, while travelling, to pay 50% on airbnb and then the rest in cash? ..
Update: Accepting cash payments seem to be secure as the traveller can pay half and have airbnb security on that side, while still having more security in terms of being able to check the housing and do live transaction. Host in turn can refuse to give keys to somebody of suspect. So in the light of these - does airbnb close accounts on violation, if the only violation is that they were prevented to collect their full part?