If bank notice your 50k in and 50k out, they might notice IRS and other agency about possible money laudering. Then you will have to prove the money is clean (notice if your friend's money is not clean, they might not support you). Then you will have to pay income tax. The gift tax exemption is 10k per person per year, means one person only can give one person 10k tax free, you have to pay tax for the remainder.
50k is not a small amount, be careful.