Relationship Stage: Many experts suggest that couples should be together for at least 6 months to a year before moving in together. This allows time to build a strong foundation and understand each other's habits and compatibility.
Clearly stating your interest, discussing your future together, and introducing him to the ideas and routines of cohabitation are some of the ways to make sure that you are both on the same page before moving in together and to increase your chances for happy and successful cohabitation.
Legally, yes, he can do so, unless there's a court order that prevents him (usually temporary orders during the pendancy of divorce, etc...). Otherwise, a home is owned by both of you, and you BOTH have the right to allow others to move into the property, even without the other's consent.
If you have a place and your landlord approves of an additional occupant, your partner can sign your original lease and become a cotenant.
The only way you would be entitled to a share of the home is if your name is on the title deeds or you can prove that you have acquired an interest in the property. You will also normally have no right to stay in the home long-term, unless you have a tenancy agreement or 'licence to occupy' granted by your partner.