4 month Lease Assign advice

New to this and fairly new to New York and the States Looking to assign the final 4 months of my 12 month lease. Landlord has given the green light providing I find someone with a satisfactory credit report and sufficient income via pay slip evidence It seems other renters are in the same situation and advertise as "in contract" "no fee" but they do not seem to state the assigne period until lease renewal... Is there a reason for this? Are there any snags I should look out for? It seems that open houses are the best way of doing this..any advice will be most welcome