I believe the ATP “guaranteed flight instructor job” is only guaranteed for those students in the complete zero-to-hero program. May want to verify that before committing to anything. That guarantee also means you get to sit in the home office answering phones till a flight instructor job opens up somewhere. Last I called and inquired about it, the pay was around $8.50 an hour.
Do you have a military aero club nearby? The ones I have seen are cheaper than the local FBO's and were part 141 instruction.
Good Luck.