I see Trump applying fees to the billions illegal immigrants send back as remittances and higher fees for immigration visas to pay for the wall. I don't see him seizing personal property to pay for it, due to the bad press such stories cause and the ease by which people can pack up and leave.
No one is going to check the papers of people taking a moving truck to Mexico and take their furniture to build a wall. That is liberal hysteria, whereas the people murdered by drug gangs populated by illegal immigrants never get their attention or sympathy. I would like to see Mexico billed for the cost of incarcerating their criminal immigrants, but that's something that will take time.
Regarding the wall: Many illegal immigrants are unbanked, so there isn't much that could be seized financially. And from Western Union to international bank accounts to Bitcoin, they have ways to launder the money / send it home.
Those who have bought houses, cars and other assets could sell them, albeit at fire sale prices. Given the sheer number who have American born children and spouses, asset transfers to citizens are a viable workaround for many.
I don't like the idea of using civil forfeiture against illegal immigrants, because it is already so prone to abuse against citizens. The last thing we need is police who already stop out of state travelers on highway and say let us take all the cash or we arrest you as suspected drug dealers getting the added power to do that to anyone on the street with cash in their wallet and lacking a specific ID card.