"Also the job is 100% onsite"
That job might still require you to visit multiple sites.
The question are:
- how many days a week will it be needed?
- How many miles a day?
- If all the sites are all local, where are they specifically?
- what is the reimbursement rate?
This might be legitimate, depending on the position. I have know people that had to provide support to multiple sites in a few mile radius. Others put hundreds of miles a week. Some people had to drop of a package of documents at headquarters every few weeks.
The office you will be supporting might not be a place you can take public transportation. For example the military base is 10 miles from the main highway, and the office is another 5 miles from the front gate.