Can I marry an immigrant and send for him if I'm on welfare and have section 8 housing?

Yes, but they will not be able to become a citizen because you must prove that you have to ability to support them financially.

What do you mean by 'send for him?' I hope you aren't falling for some online international marriage scam.

It depends on your income and the size of your family with dependents. If you have other dependents check the 2011 I-864P and it will list the income requirements.

If you don't meet the USCIS income requirement for a family of 2 (don't know your family size) of $18,213. You can get a joint sponsor. There are other ways, such as the asset test if you have savings and other liquid assets, but its generally easier to get a joint sponsor.