Create simpler workflow tool (excel/database)

Looking for someone to build a simple workflow tool for a small company operating short term apartment rentals (15 properties). Ideally the tool would:
- Hold booking info
- Create invoices from booking info (from a word template into pdf)
- Be accessible online (from different locations - poss thru Dropbox?)
- Hold a tasklist
- Hold a contact list
- Hold/show availability

I'm not sure how this would work, possibly created from Excel or Access.

Project not urgent but would like to get it going ASAP. Please send any questions, or happy to discuss.