Nick Siegler with Porch Light Home Inspections.I use him primarily due to his attention to detail, leaving no stones unturned, and speedy efforts to get the report conducted and presented within 1-2 days of request!

Or is there a different system I should implement?

Move on, and avoid letting fear stop you from looking at opportunities to implement your plans.

You can pre wire motion lights, then slide the wire thru the wall from the outside.

I have successfully implemented the program.

@William Coet, there is a lot going on with this potential scenario and I want to second the other advice being given here -- tread very lightly with specific tax advice for specific transactions, especially with seller financing. 

Here's what the quote covers:- Conversion of 2 bedroom, 1 bath main house to 3 bedroom, 2 bath (~1040 sf footprint)- Demolition of existing walls (existing dining room wall, wall between kitchen and living, bathroom closet)- Finished Shell (Reframing opening to living room and kitchen, shifting openings for bathroom/bedroom, new walls at bathroom and dining, level - Replace all aluminum windows with fiberglass windows and screens- Upsizing plumbing, and relocating fixture locations as necessary- Upgrading electrical panels- Assume heat pump and ductless mini-split for heating and cooling- An allowance for kitchen appliances including combination range, hood, dishwasher, microwave, refrigerator, and washer/dryer- An allowance for mid-grade plumbing and lighting fixtures (Delta, Kohler, or equivalent)- Mid-grade plumbing and lighting fixtures (Delta, Kohler, or equivalent)- Ikea cabinets or equivalent with solid surface countertops, includes island- Assume solar system to be installed on the house including battery storageFor the garage ADU, the garage would need to be demoed and rebuilt, but we would benefit from building within the setback since the garage is on the property lines.

Or what methods have you implemented to keep track of information and staying organized?

If during inspection it turns out to be a light repair, great--you've accounted for that. 

When  need to ask themselves hard questions about whether they will do what it takes to reach the level of success they envision and also be realistic about what strategies they are implementing to achieve their level of success.