How to correctly setup this relationship and database schema for this problem

Cant seem to wrap my mind around this...

Purpose:
Company to upload Jobs into system and allow Vendors to bid on job
items.

Quick rundown:
Company creates new job, part of that creation is uploading .xls of
list of job items, in that .xls we have a column called 'type', (each
vendor chooses which 'type' of job items there company accepts) after
job saved and job items uploaded the page goes to an invitations page
where even though a vendor has already pre chosen the types they
accept we want to be able to manually say Vendor A is invited to view
Type A, Type B, but not Type C and so on for each vendor. After each
vendor is invited to view this specifac job and its job items types
then they get emailed telling them of the new job and its items added,
they login and bid on each job item that they are allowed by the job
item type.

So far...
Jobs Model - title:string job_number:string description:text
Jobitems Model - job_id:integer type_id:integer ...... all the other
fields
Vendor Model - name:string address:string all that stuff
Types Model - code:string name:string ( code is the abbreviated
version of the name so P for Plate)
types_models - type_id:integer vendor_id:integer
(has_and_belongs_to_many association for Types and Vendors

Cant figure out:
How to setup so that each jobitem has many vendor invitations by the
jobitems 'type' and how to allow only invited vendors to see each
jobitems by the type