To prepare proposal you need to have a good understanding of user need in terms of the following
1. What they want
2. How they want
3. When they want
4. Who want it
5. Why want it
Answers from all the above questions will be derived from Interviews, Tenders document, Discussion of team mebers etc.
Once the info are gathered then need to identify their budget. Most of the custommer prefer to have more function with less cost. So, first need to identify the essential deliverables. They based on time line do a reverse calaulation in terms of resources and dependecies. Always add additional 10 to 15 % percent of resource as buffer.
Then identify the tasks of DWH and estimate resource for each stage. As per my experience Data quality, Cleanising and ETL will take almost 35% of the time of the total project.
So the business understanding and Source system data is very important. Also how good is the quality of source data also add cost to proposal. So a lot of factors are involved and there is no single direct docuemtn for all projects. So you need study the requirements or expections before prepare proposal. I hope this will clarify your details. If you need more details then pls provide me the project details, so that I can advise you on it on more detail.