I was thinking to change numbers for maintenance at the very least because this tends to fluctuate depending on varying factors.

I've personally never seen a good builder take 10-months to build anything...that is forever...if that is your timeline, you will also have materials price fluctuations...almost guaranteed.

@Branden Drebing HOA costs are big given how much they can fluctuate, even for similar type properties in the area.

You can also try using a temp gun along the path of the duct on the ceiling to see if there are sudden temperature fluctuations.

Is there other options besides HELOC that would be wiser, more affordable, and not a fluctuating interest rates??

All this to say that with fluctuating material costs and lead times it's reasonable to set the expectation early on that he should be reporting costs and submitting change orders--and also what will happen if it isn't handled correctly.

Because I'll tell you, that will fluctuate.... for sure.

I am happy to accept this, because I know his income fluctuates in the winter.

Or it could also be bad breakers (check if it's only happening on certain circuits), defective electrical service supply/voltage fluctuations (unlikely unless the whole neighborhood is having the same problems), service entry wiring defects, a loosely connected neutral or other issue with the neutral, loose connections anywhere in the circuit with the flickering lights, or a number of other things we wouldn't know without being able to inspect the system. 

Last month.....price don't fluctuate that much typically over the year...like the cheaper ones sell in November and the expensive ones sell in July.