Word also offers built_in table templates that enable you to insert pre_formatted "Quick Tables" into your documents. To insert a table using one of Word's templates, choose Insert > Table > Quick Tables and choose the template you'd like to use from the gallery. When you click on the template, Word will insert the pre_formatted table of your choice.
You can look online for sample proposals that you can work from, in many cases you will be able to download a template that you can work from. You will most likely find that there are dozens of sites offering hundreds of different templates to download. It may take a while, but you will find that there proposal forms that will match almost any need including yours. Take your time and select the one that best suits your needs.