Just found an inexpensive way of getting a contour map, thought I'd share. It uses LiDAR data, which is very accurate.
It's a 2-step process, A) Getting the LiDAR data from the USGS, B) Converting it to a Contour Map you can see on Google Earth.
A) If you go here, you can see if the gov't has LiDAR data for your place:
http://earthexplorer.usgs.gov/
1. Type in your Zip Code in the box for "Address/Place."
The box is located in the left hand column, under "1. Enter Search Criteria"
2. Drag the marker to your farm.
3. Click the tab for "Data Sets" at the very top row.
The tab is located next to the "Search Criteria" tab.
4. Select "Digital Elevation", then select the box for "LIDAR."
5. Scroll all the way down, then click the "Results" Box.
Then select the download icon to get your LiDAR file.
B) After you have the LiDAR download, you can hire this guy (adrrian.diaconu@gmail.com), he charged me $22 for converting the data into 2 contour maps. For my place, 60 acres, I had to download 2 adjoining tiles of data, which he spliced together for me and made the contour maps to the specs I gave him.
And nope, I'm not getting a kickback, I hired him from Upwork after I got frustrated from hours of looking at Youtube videos and downloading free software. Finally gave up and the $22 was money well spent!