Two trades pour footers for a manufactured or mobile home: a mason, or the grading and site-prep contractor who is already on the lot. Many do both.
Short answer: Footers are the concrete the home sits on — poured footings under each block pier, or a perimeter footing for a pier-and-beam setup. The layout comes from the home's installation manual or an engineered foundation plan, not from the contractor's preference. A mason or a site-prep contractor digs and pours them; the setup crew then sets the block piers and the home. Your county may inspect the footers before the home is set, so ask before you schedule the delivery.
Reviewed by a manufactured home setup contractor and dealer.