Dad's Money Flow — By Uber Hours

Set "scale back after month" to 0 for single-phase (no scale-back). Otherwise, Dad runs at initial pace for that many months, then drops to the new pace for the rest of the 24-month window. The auto-replacement reserve recomputes based on blended mileage.

Vehicle cash cost = fixed + variable (variable scales with Uber hours). Loan / rental / insurance are fixed each month regardless of hours. Fuel, electricity, and per-mile maintenance scale linearly with hours driven (70 hrs/wk = full variable cost; 35 hrs/wk = half; 0 hrs = none). The slider auto-updates when you change hours or pick a vehicle preset; drag it manually to enter Custom mode.
Grandma's car: $0 fixed + $1,400/mo fuel at 70 hrs (≈$1,000 at 50 hrs, $600 at 30 hrs). Avis Premium EV: $1,525 fixed rental+tax + $175/mo electricity at 70 hrs. Tesla NEW: $933 fixed ($583 loan + $350 ins) + $267/mo variable at 70 hrs ($150 electric + $50 maint + $67 misc) = $1,200 at 70 hrs. Tesla USED: $1,102 fixed ($752 loan + $350 ins) + $200/mo variable at 70 hrs = $1,302 at 70 hrs.
Replacement fund = depreciation set-aside (separate savings bucket for the next vehicle). Auto-scales with Uber hours and scale-back settings when a Tesla preset is active.