@Lei Zhao I think you've made a good decision by selecting Indianapolis as your starting point.

I think if you really need the property to be between 15 and 20 units, then you'll have to be willing to look throughout the entire market to have any real selection.

Site Selection, 2.  

Screening and being selective is the key to staving off problems.

Make sure you can develop a team in whatever market you choose and select a great real estate broker who can connect you.

The bookstore has some great books and the podcast is full of valuable information.Find and connect with other BP members that are in your area: https://www.biggerpockets.com/search/usersSet up keyword alerts to be notified of the topics that interest you: http://www.biggerpockets.com/alertsRead Beginner’s Guide: http://www.biggerpockets.com/real-estate-investingCheck out BP Podcasts: https://www.biggerpockets.com/podcastIf you wish to tag someone in the conversation on the forum, type @ followed by their name and then select the name of that person which should appear below the comments box.

It doesn't have a selected flood map boundary.

On the flip side, you forego the control of selecting the individual properties.

You can also try clicking on the tab "Network" on the BP Toolbar and select "Mortgage Lender."  

Last part goes without saying, but select an agent and build an exclusive relationship.