see also spareroom.com
You should inform your mortgage co and insurer and get written consent (ie you may not be covered for theft by lodger).
Get them to bring a passport, get a company reference is possible – see works pass etc, take a photo if no passport, note their car reg no etc etc.
Understand that the deal cuts both ways, it’s THEIR house as well as yours Mon-Fri, clearly state and agree boundaries, house rules etc before move in.
See HMRC website re rent a room scheme.
Understand the term ‘resident’ in relation to Council tax.
Invite them round, have a mate for opinion #2, always tell them that sombody else came first and they have first dibs(*or have another excuse to turn them down if you don’t like the look …)