How much is the average cost to drywall a house and does that cost cover taping and mud, and
Sanding?

Drywalling an entire house will depend on number of rooms, drywall panels that will be used but should include the taping and mudding and make ready for just the texture and paint.

This average will vary significantly between different areas of the country and level of expertise that you hire. Additionally, if you live in an area where workers are unionized, you will pay more.

The best bet is to call around and get an estimate of your local area.

In my area most guys charge about $9-10 per sheet to hand tape and sand, materials not included. They really great guys do almost no sanding and can blend in the edge with a damp sponge.