I could set up a company that would, in exchange for buying $3000 of my plastic toys, hire someone and let them resign a month later.
There are ways to prevent that. For example, the government could require that (a) the employer sponsoring a new immigrant has to pay six months of the immigrant's unemployment insurance in advance (perhaps put into an escrow account), and (b) if the immigrant is neither employed nor collecting unemployment insurance for more than, say, two months, then the visa is terminated.
Another possibility I've seen floated is that the government make only a fixed number of work visas available, but auction them off. Then the immigrants let in would be the ones who are likely to add the most value to their employers.
Actually that's also how we solve it in Canada for relatives of immigrants. In order to bring kin over into Canada one must sign a commitment to cover their social welfare expenses (if any) for a period of 10 years. This has done wonders to curtail people bringing in elderly relatives who do nothing but sit on welfare checks. This also holds someone accountable without leaving someone behind.
There are ways to prevent that. For example, the government could require that (a) the employer sponsoring a new immigrant has to pay six months of the immigrant's unemployment insurance in advance (perhaps put into an escrow account), and (b) if the immigrant is neither employed nor collecting unemployment insurance for more than, say, two months, then the visa is terminated.
Another possibility I've seen floated is that the government make only a fixed number of work visas available, but auction them off. Then the immigrants let in would be the ones who are likely to add the most value to their employers.