We recommend you arrange as much as possible before coming, at least have friends or host families to accomodate you for a few weeks. It's harder to find good bargains in a hurry, AND most rentals are taken by Fall term (mid-September).
A big part of expense is the rent and another big part is for food. If people can cook themselves, they will at most spend $250/month. For those who cannot cook and need to go to restaurant for every meal, they may spend around $600/month.
LTD bus is free with student ID. Usually 7AM to 11PM, one bus per half-hour. Bikes are common and sometimes even more convenient than cars. Try to stay on "pedestrian & bikes only", or bike lanes whenever possible, for your safety.