My answers

最近刚刚开始有section 8的租客，很奇怪他们都是section 8 cover所有的rent. 我以前听说section 8只cover一部分租金，需要自负一部分。但是我的租客好像都是一分钱也没办法付房租的。 这是怎么一回事？

1. if they work (or getting child support, etc) they have to pay according to what they have. Your tenant has no nominal income except welfare (although every single mom has some guy living with her....that's just part of the system no body cares)

还有就是section 8如果要涨房租的话，是不是只要求涨到Fair Market rent, 就一定会批准？ 是不是要在一年lease结束前提出request? 现在刚签的lease price比本地区的Fair Market rent要低一两百。

2. They have their guideline each type of unit shoud charge how much, the numbers is usually a little higher than the market price. Your request to increase rent below this limit is not always accepted because you are dealing with a bureacracy. Then you have to make it clear whether you want to keep the tenant at current rent level. 

I have very few Sec 8 tenant because I hate the annual inspections. They will always find something wrong for you to work with, which is the tenant's fault.