@Todd GoedekeA properly configured self-directed Solo 401k plan will also provide checkbook control.  

Even whatever you may consider to be a "standard" garage (or whatever) is going to vary widely in cost based on things like the specific lot conditions, and *all* remodeling is dependent upon the size and configuration of the building, at minimum. 

Site descriptionSite description includes facts about location, configuration, topography, drainage, soil and subsoil, hazards, easements, deeds, restrictions, encroachments, access, utilities, and zoning.Improvement descriptionsQuality standards for foundaion, exterior, interior, windows, doors, lighting, HVAC, fire protection, parking, ADU, and functional utility specified in construction details and specs.Project viabilityThe economic viability of the local area is essential to the project's success.

Get that configured with bookmarks and be religious about checking in.Good luck

The city even ordered the owner to do an impossible, irrational thing -- to restore the one-bedroom units to their original two-bedroom configuration -- which would have required ripping out walls, kitchens, and bathrooms, and displacing all the tenants, at a huge cost that would actually reduce the future rental income.

Vacancy, property repairs and owner paid utilities are additional required factors but can fluctuate throughout any given year based on market conditions, property age and configuration and tenant mix. 

Parking spaces may be configured on-site per state law.No change in parking requirements for the ADU.Replacement parking for garages and carports converted to ADUs will not be required.Junior ADU(JADU)Not allowed.Allow JADU up to 500 square feet within the existing walls of a single-family home.

From my experience it really depends on which city you are in.In certain parts of London lots of houses have been converted to flats of various sizes and configuration, so there can be quite a discrepancy.Though I think now they are using the FOR SALE brochures to get Sq footage and other details then use that to update property details so it's getting more accurate.

If this is to be your forever house, you may want to look at fibreglass framed windows as they provide a better thermal barrier and resist deformation a lot longer than vinyl ... the trade off is they are rather more expensive and the most experience manufactures {of whom I am aware} are located in Canada or Europe ... though I'm sure there must be manufacturers in the U.S.A.Another general guideline is to use as many fixed windows as possible ... they are cheaper and more energy efficient.Where an operable window is required, casement/awning/hopper windows are far more energy efficient than single or double hung and sliders are at the bottom of the heap.If you take your plans and lot orientation to a fenestration specialist, they will conduct a solar profile of the property and can recommend window and door configurations for each face.  

There are so many ways to configure your tech stack but I value simplicity and efficacy.