The answer to the what to charge question has two parts:
How much to show-up? Anyone in the business of driving around to properties in these days of rising transportation costs needs to be keeping track of vehicle costs and reviewing them frequently. Figure more than just fuel costs. You need to include auto insurance and vehicle replacement costs.
What is your hourly rate? This is a tougher question. But you know what hourly rate you've been paid in other jobs. The difference when you are working for yourself is you need to figure out what accountants call a "burdened" rate. That is, a rate that includes paying for marketing, health insurance, camera equipment, retirement and all the other costs of making this a long term sustainable job.
What's the competition charging? It goes without saying that knowing what the competition is doing is always an important part of the what to charge question. Take care when doing this. You have to also compare the competition's services. Studying the competition's prices and offerings needs to be a regular exercise.
The recent what do you charge poll: The graphic above shows the results of a poll I did recently on what real estate photographers charge. This is a 100,000 foot level view of prices because the people voting were from 110 different countries, 67% US, 7% CA, 6% AU etc. All presumably converted to USD before they voted, this only gives a general feel of what the range of prices are. It's more important to make sure you are recovering your expenses and making a fair wage.
The big city effect: Since I spend time in Seattle, WA and Salem, OR I've become keenly aware of the difference of what services between Seattle and Salem. Everything in Seattle cost twice as much as it does in Salem. This location factor effects what real estate photographers can charge as well. In big metropolitan areas real estate photographers need to charge more because it's more expensive to operate whereas in sleepy rural areas you'll need to charge less.
The effect of marketing: I think the effectiveness of your marketing is an important factor that is over looked because photographers like to photograph better than they like to market. If you do effective marketing and keep your name in front of your potential customers you'll get more business at a given price than if you just sit back and wait for the phone to ring. This factor, I think is more important than keeping your price low.