I'm pretty sure most serfs were renting pre-existing dwellings.
And I'm not sure what you're getting at with this welfare state stuff. Yes we get taxed and receive things in return but so did the serf. The only difference is the serf typically only paid one tax for everything that also included his rent. Currently, people are paying the same amount as the serf did just for rent (30-50% or more) yet the landlord has no responsibility to maintain roads and any of the other basic services he did back in the day. Instead the worker has to pay for these things on top of what he is already paying the landlord. The only benefit the modern worker is getting over his medieval counterpart is better quality housing.