HR and such software is rarely developed from scratch. But let's go with this. That is, you are wanting to hire programmers and designers to build your new hire process apps and database from scratch.
This gets even more expensive as "from scratch" means you won't use any ready to use database like MySQL in spite of it's no cost and in use by millions.
So I think you need a system architect, then a team for the database backend then another team for the app the HR users will see.
Maybe you didn't really mean what you asked but in the USA I'd peg such a system if you want it to be on par with what you get off the shelf today to be in the 100 Million buck development range.
Figure at least a year or two.
I need some ideas and ways to approach a new hire process that will need to be built from scratch. From forms to emails, signatures from managers and process flow. Just gaining some high level ideas at this point. I appreciate any feedback.