RE: Business Proposal
Business proposal ... as in a partnership agreement for the co-owner ... or for that matter an offer to purchase document for the current owner? ... in either case this is a specialized document that you should draft carefully and have reviewed by an attorney to be certain of protecting your interests.
If you mean business proposal as in "business plan" ... two points ...
1) a business plan is a working document ... the plan should be neither simple nor static... it is a dynamic roadmap which you use, revise and refer to constantly.
2) a business plan being used to obtain funding needs to be to the satisfaction of your financers. The plan needs to be written one way for bank financing; where the banker is interested in the protections provided to them should you fail (just like any other loan) ...
Whereas most "equity" financing, where you are giving away a piece of the action or equity in the business, tends to be more concerned with how they will recieve their money as you succeed (success is the assumption they operate from ... otherwise you would get nothing from them).
Reading at Borders or Barnes and Noble is an excellent way to undertand Business Plans. You can help to improve your chances of success by spending a good week visiting those book stores and reading for many hours on how business plans are constructed and used.