The only ones who wont be exactly the same as before will be from the EU and they will be able to come as tourists just as we will go there, if they work they will get caught out unless they work illegally for peanuts, and that isnt going to be huge numbers in reality is it and they could just come via Calais far easier and cheaper in any case,if you rent them property as the landlord you have to get proof they are here legally.OK, substitute YOUR use of 'illegal' with 'legal'. It will not necessarily be legal once we diverge of course. Control of immigration is one of the flagship Brexit 'benefits' after all.
I have yet to see ONE reason why we need to put a hard border in that stands up, milk movement is one that will need a check if tariffs come in but even that can be sorted by knowing where each producer is selling his milk, yes there will be some smuggling but there always was