Tenate wants to move in his jobless friend

[Johnny Fullerton]

One of my tenates (single guy in a 2 bedroom) asked if his friend "that fell on hard times and lost his job" move in with him. I sent out an rental application form for him to fill out cause I do plan on screening him, but if I do accept should I rewrite the current lease and just add both people on it; or should I just leave it up to my original tenate to figure out their own payment system as long as I get my rent. I also want to raise the rent an extra $50/month. The original tenate I have no complaints about, but should I even consider his friend as he told me he is in between jobs.