Different ways of building a home

Hire a luxury builder and use a customized design, $250/ft2
Hire a custom builder, $200/ft2
Hire a builder and select one of their designs, $160/ft2
Owner as builder to manage the project, ideally $120/ft2
DIY, owner and friends do most the work (sweat equity, without pay, labor hours 1-2hr/ft2), $70/ft2
Numbers are for illustration only as actual cost varies. Land cost not included.
DIY home building
DIY build potentially could be lowest cost. Optimal design should target:
Incremental home building

Phase 0: buy land say 1600 ft2
Phaes 1: build 200 ft2 home. Building coverage ratio 12.5%. Floor area ratio also 12.5%.
Phaes 2: add 200 ft2 next to it, in this case as a garage without air conditioning. Building coverage ratio 25%. Floor area ratio is still 12.5% as a garage is not included in conditioned floor area.
Phaes 3: add 400 ft2 2nd story, to 600 ft2 floor area. Building coverage ratio 25%. Floor area ratio 37.5%.
Phaes 4: add 400 ft2 to the side, to 1000 ft2. Building coverage ratio 37.5%. Floor area ratio 62.5%.
Phaes 4 alternative: add 400 ft2 3rd story, to 1000 ft2. Building coverage ratio 25%. Floor area ratio 62.5%.
City of Houston code requires one parking space for 1000 ft2 single family dwelling unit when parking is required.
Incremental construction reduces time and money required for each phase, making homeownership easier and earlier.
More efficient use of space for lower cost
Time sharing building use
Flexible use of single family home
Starter home community and courtyard style option

25'x50' is close to the smallest size lot in the city of Houston. To maximize single family home width in 25' width lot, side setback may be 1' one side and 3' the other side for 21' width of building. 1hr fire resistance rating is required for the exterior wall as setback is less than 5'.

Shared courtyard among several homes allow big yard when land area for each home is small.
5' private backyard is an option with up to 4' see-through fence.
Kids can play in the courtyard and adults in the homes or backyards can watch.
Construction loans
Some lenders provide construction loan, including buying the lot, some automatically converted to permanent loan after construction is completed, called one-time close construction loans. An approved builder and detailed plan would be required. Down payment could be as low as about 4%.
The difference between buying a home built with investor money and built with construction loan on the home buyer is about 30%, as investors need the 30% markup to cover profit and risks. Risks include construction delays, cost increases if passed to investor, builder failures, failure to sell in the expected time and price, etc.
Self-Help Homeownership grants and loans