Build a Property Management Solution for vacation homes front and backend -- 2

We are in need to develop our own Property Management System to manage a portfolio of holiday vacation homes. The system will have a good front end similar to the one we currently have (which we are completely changing as we are changing providers) The typical front end for vacation home rentals will be there plus the ability to manage the full range of properties issues in the back end including maintenance, owner managment, simple reports, adding deleting properties, calendar syncing with ICal two ways, send emails to cleints, manage client databases...etc The system will be integrated with MIGS for payment gateway and will link to an API for a channel manager (API is simple and has details about the properties, calendar, guests, reseration ..etc) this API will live sync two ways with this channel manage who provides the API specs. The API file will be shared with the winning bid. The admins should be able to fully manage specials, add delete and modify calendars, rates..etc Local maps will use Google which will take from the input of the admins