Modular is great in places where labor costs are high, and maybe if you're building to the dimension of shipping containers/trailers so that it can be easily transported and pieced together.  

I started out in high school getting up at 5:00am each morning so I could get to school early to practice my trumpet, I then stayed late to be on student council, I was in the band, a political after school club, I worked two part time jobs, and had a girlfriend.

Personally, if it's in a A, B and some C neighborhoods, I install central AC in mine.

With the crash, we snapped to the other extreme and that's where we are today, and the rubber band of the market is pulling things up, and will continue to do so until we near parity. 

If desired, the energized 'social scene' of every dimension is just down the road in Santa Monica. 

The dimensions given are all liner, 30 feet X 24 feet, that must be converted to VOLUME, 6 inches thick because concrete is sold by the (cubic) yard.For practice ask an agent, or a friend for a copy of a filled in contract and executed HUD 1.

Should I order custom windows to give myself exact frame dimensions of the old aluminum ones or should I save 20% by buying stock sizes that are fairly close to the old ones?

The dimension beyond the world of book writers and investors!  

There are all kinds of band aid solutions to the problem all of which do not directly address the problem.

Each property has a subaccount under a main account such as rent, utilities, repairs, etc.Rent property ARent property BUtilities property AUtilities property BAnd so on....One bank (checking) account I like to keep 3 months rent across the board in a reserve account (savings)