Hi @jhondavid,
HubSpot itself does not support mobile app development, however you can create a responsive, mobile friendly website which you can find in the Asset Marketplace.
For a solution that allows prospects to buy from you, I’d recommend checking out ecommerce solutions that integrate well with HubSpot, like WooCommerce, Shopify or Magento.
The prices vary for both website templates and integrations and they do not include HubSpot license fees. So you’d end up with a one-time fee for the template, the subscription fee for your ecommerce solution and the subscription fee for HubSpot Marketing.
Hope this helps!