You said you were going to Grad school, but didn't really say where. I am assuming its CSUS, and if you are going somewhere else my advice might change.
If you are looking to minimise rent and maximise personal safety your best bet is probably to look at renting a spare room in someone else's house. You will lose some privacy probably probably save some money. You could probably find an arrangement like that in Campus Commons or Sierra Oaks which are very safe neighborhoods immediately north of CSUS. Depending on where you live, you might be able to walk or ride your bike to class which could save you more money. Other neighborhoods that are reasonably safe near campus but a little less posh might be College Greens, where again you could probably walk or ride your bike to class.
This is a map of educational attainment in the region. It will give you a general idea of which neighborhoods are low income and where the professional people live. If you play around with that link you can find some other maps that you might find useful too. It will help to give you a general idea of what neighborhoods to consider and what neighborhoods to screen out.
STI: ERsys - Sacramento, CA (Education)
Next this is a map of the craigslist housing ads, but presented in map form, it shows where these listings are. Between the two maps, that should give you a rough idea of what the neighborhood is like.
HousingMaps
But you probably will want more detailed information. If you find a place you are interested in, look up the address here. It will tell you the last 100 crimes that have occurred with in a given radius from that address in a given period. On the advanced features, you can specify which crimes most concern you like say prostitution or gang activity.
Online feature - Crimemapper - sacbee.com
Lastly when you get ready to your narrow your search down, come back here and ask about specific areas. The Arden Arcade area is a big place. There are parts of it that are very nice and others that are less nice.
Since you asked about midtown and greenhaven. If you are looking to live someplace that is quiet. I would probably avoid midtown. It has a lot of bars, drunks and noise. It doesn't sound like what you are looking for. There is nothing wrong with Greenhaven, but its further away from campus and I think College Greens or Campus Commons or even some of the condos off Fulton or Howe like Timberlake or Woodlake might be closer to campus and be equally as safe.