That depends if want to do it 141 or 61. I f you want to save lots of cheese then do it 61. I you're good, with part 61 you could probably do in as little as 5 hours. 141 you must follow the syllabus usually 20+ units.
I did my CFI in about 10 hours of flight an 20 ground, which is pretty typical. Figure $730 for the aircraft, another $600 for the CFI. Two written tests are going to set you back $140-160. Studying every night at home, free. Checkride with the FAA, also free. Comes out to about $1500.
You might need a little more than the ten hours to get used to flying in the right seat. You'll find that takeoffs are about the same as the left seat, the flying is about the same, but the landings are strange at first. Of course, a lot depends on how sharp a stick you are. And, of course, we're all sharp sticks.
You will spend much more ground time than flight time as your instructor helps you with lesson plans and refining your shtick for explaining maneuvers and using the blackboard, etc.
$2,000 should be the top end. I agree with Part 61, although I've heard of some places who have a 141 CFI course with self-examining at the end. Best $2K you'll spend because you'll acquire a credential that will give you a chance to find work and build time sooner rather than later.
Any estimates on how long it takes to get the CFI and the commercial? Currently I hold a PPL and non-current instrument rating.
What is best way to get the ratings for tax purposes.
I figure that I can
1) Get the commercial
2) Get the CFI
3) Start teaching
4) Get IFR current (tax deductible as a job expense)
5) Get the multi-commercial (tax deductible as a job expense)
6) Get the CFII (tax deductible)
7) Get the MEI (tax deductible)
I will hold my current job. However, once I start teaching on the side, then the additional ratings should be a job expense. They won't be qualifying me for a new job.
What you are really proposing to do is finish your initial training. Although I'm not an accountant, I can tell you, sadly, that none of this is tax deductable. The IRS won't let you deduct the cost of training which qualifies you for a new job. You are talking about finishing your basic ratings, those which would qualify you for a different job. Just getting your Commercial and CFI aren't enough. The CFI-I and MEI fall under that classification. Even if you can go to work with just your CFI, the IRS is likely to look askance at your deductions. Moreover, not too many places will hire a single-engine pilot with just a CFI.
Now, expenses that you incur after you get that first aviation job to keep you employed would be tax deductable , e.g., Jepps, job hunting costs including travel, resumes, etc., uniforms, type ratings.
Finishing your ratings will depend a lot on you and the time you can put in. If you can train full-time, you could go to any of the well-known 141 schools and they can design a program under Part 61 to finish you up. You could do it Part 61 at your home airport. You might be able to do it in six to eight weeks. I gather that you haven't taken the writtens yet, so studying for those will take some time. Or else, you can go to a weekend school. You'll need to take writtens for Commercial, CFI, FOI and CFI-I. Along the way, it wouldn't hurt if you took the BGI and IGI writtens and get your ground instructor certificate. The writtens are similar to the CFI and CFI-I.