You can buy >50 gallons of RO water from a grocery store machine for the cost of the Wards test & shipping. I think downloading the EZ Water 3.0.1 spreadsheet, using 100% RO, adding only CaCl2 & CaSO4, and determining the amount of acid malt to the mash will eliminate water concerns. If you go this route, post your plan in this thread.
The up front cost to treating water is:
<$15 gram scale (also handy for hops and acid malt weighing)
<$2 2oz jar of CaS04 (gypsum)
<$2 2oz jar of CaCl2
<$3 50 tablet jar of campden tablets (1 tablet = about 0.65 g and can treat 20 gallons, ratio as much as you need for your water)
You'll still want this stuff if you go through with the Ward testing and end up mixing your tap water. I think it's cheaper and easier to buy some RO water from the beginning and think about tap water later.