Can you tell me some good websites for genealogy research? I'm looking for options that are free or low-cost and will help me outline my family tree. Also, it would be great if the site has an app. I'm looking to start by researching United States records/ancestors.
I found some genealogy websites that match your criteria.

1. FamilySearch.com- Extensive genealogy database It is free to use, helps you create a family tree, and has a mobile app. Good for the United States and global research.
2. MyHeritage.com- Contains billions of records and provides automatic matches to other family trees and records. 14-day free trial and then $12.46 a month thereafter. It has a phone app. It supports United States record research.
3. Ancestry.com- Large database and provides account holders with family tree building and suggestions. It has a mobile app, but it is not free. It has a two-week free trial, and then you can pay $21.99/month with a 6-month sign-up for access to all U.S. information. However, there is an Ancestry Library Edition you may be able to get for free through your library.