The Martian surface is exposed to 7.6 REM per year - and with 25 g/cm2 of ice (water or CO2) you cut it back to less than 0.26 REM per year. Ice igloos are easily made from available resources with the interior lit to Earth normal levels throughout the day using concentrators and optical fibers.

Solar hybrid lighting
https://www.youtube.com/watch?v=tqb1ONw_FVA

Ice domes
https://www.youtube.com/watch?v=W3w6jMR3crM

Martian surface radiation
http://authors.library.caltech.edu/4...13_FINAL.pd f

Indoor farming
http://edition.cnn.com/2016/09/05/wo...ndoor-farming/

Solar conditions on Mars
https://ntrs.nasa.gov/archive/nasa/c...9890018252.pdf

With a surface gravity that's 37.7% that of Earth, dome sizes can be far larger than on Earth, making very large structures possible.