I'm not familiar with Menard's.
It all depends on what is in the kit. If the kit consists of all pre-cut framing, siding, and roofing bundles, it may be a good deal, but there will be materials you may need to buy, such as electrical wiring and panels, plumbing pipes, and the like. I checked out your link and saw nothing about the deck being included. Your husband may also prefer not to use some of the materials in the kit, such as conventional nails. A nail gun sometimes requires different nails, but the higher expense of the nails may be outweighed by the time and labor savings of the nail gun.
You may be able to get the same savings from buying a blueprint that suits your budget and needs and then getting a materials package from a conventional lumberyard. More labor, of course, as nothing will be pre-cut.
I have noticed that in all the outbuilding kits I've seen recently that the materials go down in quality and factory construction when a kit is purchased that is highly factory done and requires little construction by the purchaser. In many of these buildings, I think a person is ahead by buying a blueprint and constructing the shed conventionally. In the end, both sheds would end up costing about the same, but the owner-built shed would be higher quality if a person has some building experience. Hiring a good carpenter to do all the critical stuff with assistance from the purchaser would also result in about the same overall cost.
But a home isn't a shed. You may have real constraints to consider; besides the financing, you will probably have some county ordinances that will have to be met to obtain a building permit. Construction always runs more than anticipated, every time, to some degree, so it is better to over-budget than vice versa. Same goes with financing; if you can only borrow so much and no more, it's better to plan for a smaller house than one that may be most appealing.
There are thousands of blueprints for sale at very low cost. An owner-built home built from blueprints can be trimmed down in size, or built in a mirror opposite than the print. Kits are more fixed in size, and there may be an upcharge for building one in a mirrored version.
Another factor is what's there on your property. You may have enough large trees to find a logger to cut the materials you need in trade for some allowing him to cut other trees for him to sell, and you may be able to find someone with a mobile saw that can cut the timber into the lumber needed in a swap for timber as well. My family did this with a cabin we built in the 90's. The cabin's materials didn't amount to much in materials costs, but we all put in a lot of labor.
I've known folks who bought land and built homes using alternate construction methods that cost almost next to nothing. One built a home for old tires filled with dirt and then plastered the interior and exterior. The house looks entirely conventional, but only the roof, floor joists, interior dividing walls and flooring were lumber, and all the structural stuff was from timber that was cut down and hand hewed onsite. The roof was sodded. Not a home for the city, but a good one for the country, and completely low maintenance with very high insulation. And far from funky looking as well.
A ton of labor went into that house - several year's worth- but no financing at all, and the home met all county construction requirements. It's also overbuilt structurally. The couple who built it didn't know a thing when they started, but both are experts now, for sure, and they have the only house in the county that has a roof with wildflowers growing on it all summer.