Some people will think that if he rents this room, he will have the right of residence and distribution, and he can add or replace people at will. But this is not the case. First of all, although the bedrooms live separately, the kitchen, living room, bathroom, balcony and other public places are shared and used by both parties. It is impossible for you to bring a person in without going to the office, so this involves the issue of cost sharing.
Secondly, after a person moves in, it will inevitably bring about the increase of various expenses such as water and electricity, which also requires clear communication with the other party and sharing the expenses.
Finally, in addition to the cost, there is also a question of living habits. For example, if two people live in the same house, it will be much quieter, then every additional person will increase a lot of noise, and the daily routine brought by this person, such as sleeping late and cooking, will also affect each other.
So this is definitely not the house I rented. I can take whoever I want to live with and stay as long as I want. This is definitely not the case. Empathy, if we choose the object of sharing, in addition to the price, we will also pay attention to the other person, what work and rest rules, what living habits and so on, because these are all important factors that may affect whether everyone can live in harmony and enjoy life in the future sharing process.
As for how to share the expenses, I think it is necessary for both parties to communicate with each other, and there is no fixed sharing ratio for reference. In fact, if you and your roommate are good friends and are generous, he will be happy for you to bring friends and won't let you pay more. This is also feasible. You can invite him to dinner or make it up to him in other ways.
This has happened to me before. Another roommate brought her boyfriend to live with her. I was a little unhappy at first, but I soon felt that after her boyfriend came, it also brought us a lot of convenience, such as repairing the light bulb in the toilet, and everyone got along well, so the matter was dropped. In fact, sharing a room is fate. With more respect and understanding, life will be better.