PropellerLeads allows Salesforce Users the easiest, fastest and the most robust way of having multiple Contacts per Lead:

> No more pain with having multiple Leads per Company

> Absolutely FREE and fits 99% of Salesforce Organizations

> Supports Professional Edition

At the moment there is no quick and robust solution for using B2B Leads in Salesforce. There are a couple of ideas / suggestions that could give you the ability to have multiple Contacts per Lead, however all of them require spending resources for building a solution that would meet, at least, basic-level requirements.

PropellerLeads is absolutely FREE application, that runs natively on Force.com platform on Classic and Lightning environments. It is not just giving you the ability to use multiple Contacts per one Lead record, it also contains some background logic that automates several business case scenarios, including changing Primary Lead Contact information and, of course, conversion with transferring ALL the B2B Lead Contacts to the new Account record respectively

BTW, starting from v. 2.17 the app provides the ability to choose: Contacts or Prospects (custom object that mimics standard Contacts).