It depends
How large is your HMO?
Will it change licensing or safety requirements ?( eg from four to five occupancy )
I personally charge the person for a full room and block that room so I’m not pushed into a different licensing bracket
If it does not impact you you could charge 30-50
%
You need to consider wear and tear to that room and the impact on other tenants in the HMO
I’d the house full ? Do they mind an additional body in the house etc ?
You could lose good tenants accommodating one
If the wife is a short term guest then its up to you if you want to charge. You should probably get some sort of signed agreement that shes not going to beckme a permanent resident and the date onwhich she will be leaving to cover yourself.
Im assuming you live in the same property and share living space. If you own the house then you can have 2 lodgers before the property beckmes an HMO. If you rent the house, its one.
This sounds a bit strange to me why is his “wife” not already living with him where is she currently living and where will she be living after the “few months”
Is she coming here from.abroad in September? If so is she “officially” staying with him and how likely is she to return/leave after September
It may seem obvious but the fact that his “wife” dosent live with him although possibly sounds ideal to many a married man seems a bit odd