The lease is definitely a good idea. I'm not sure if you live together with his mother but if that's the case you should take things that are mailed to that address with both of your names to the AOS interview i.e. magazines, letters, etc. Also, if you all have cell phones add each other to your respective accounts. Have tons of pictures and items if you all have traveled or gone to events i.e. tickets to a concert. Hope this helps.