First, even without trying to rent, you would benefit from working on improving your credit. My 'Go-To' person here in the Sacramento area is Heather Champlin at Blue Water Credit. She can be reached at (916) 315-9190. They will give you tips you can do on your own to improve your credit, but also if you have erroneous reportings, they can help you get those corrected.
In terms of paying at one time....I have a couple of thoughts. Did you know sometimes physicians make terrible tenants? (at least in my opinion on MY properties). The reason I feel that way is that they make great money but do not know how to care for a home. They spent all of their time in medical school and working long hours. They don't focus on responsible maintenance of a home.
So paying for a whole year up front may guarantee the rent payment is made throughout the year, but does nothing to show your responsibility of maintaining the property. The credit report is more than about your ability to pay. It's your demonstration of being responsible of paying your bills, each and every month, and on time. That takes discipline and responsibility that would also possibly reflect on your care of the home while you are in possession of it.... more