You can do research for available homes for sale . For listings you can go to this web site, trulia.com. However, not all listings are current. and this can be seen by, after seeing a certain listed property, scrolling to the bottom of the page and looking to see if the dates are current.
For the purchase of a home this often requires a loan. One of the first steps is figuring out what loans people or families can afford. Often the purchase of a residential home to live in is with a 20% down payment and a 80% loan. Here is a link to my other real estate web site that has a page with a mortgage calculator to help you figure out the monthly payments.