Student assistance is OK; you can still sponsor. To sponsor a spouse there is no minimum income required. However, the visa officer processing the file will want to see how you two will support yourselves once the applicant has landed. So include your plan of what you will do - where you'll get money, where you will live, etc. - in the application, with any proof possible. If the applicant has good qualifications and can speak English well, mention this. Show any evidence of any savings or investments either of you have. If your parents are going to be helping you get settled, or letting you live in their house while you look for a job, then get them to write a letter explaining this.
It doesn't happen often, but people can be refused if the visa officer does not believe the couple will be able to support themselves. The one case I remember is: the husband was a recent PR himself, from China, and was working for minimum wage; his wife was from China, could not speak English, and was a teacher there, so would be unable to get the same type of work here. The PR visa was refused because the visa officer thought they would have to go on welfare.
