prospective tenants - tenancy amendments

Tenancy Types and Management

Currently my property is getting lots of interests from prospective tenants

However I'm also getting interest from prospective tenants whereby a couple want to move in, however initially 1 person is moving into the property, while their wife will join them after 3 months (I believe the wife overseas who is still undergoing visa approval process). Therefore I am need some advice how to procced with prospective tenants in this situation and what are my options?

I believe in this situation I have to go ahead arrange the viewing, but explain to the prospective tenant, the cost and time effort it will take to process their application. So for example for that 1 person moving initially, I would have to carry out Tenant referencing, Right to rent checks, Deposit collection, protect the deposit and then create and sign the tenancy agreement. However when the wife joins after 3 month I will have to re-do everything again - as a joint tenancy contract, which will cost me additional sum of money and time to do this again. Would I be able to charge the additional cost of these amendments to the tenant directly?

Please advise.