Since both companies make good machines, although I prefer some Istobal models, I would be concerned first with the low volume.
The reason is income dictates what you can afford to invest. Moreover, you should not rely on machine to increase volume or average sales because machine doesn’t make a market, people do.
In other words, you should have some hindsight or solid evidence the market is capable of supporting more volume at a higher price.
Assume you wash an average of 20 cars a day, 312 days or 6,240 per year at average price of $6.00 equal $37,440 gross. Less variable unit cost of $2.00 equals $24,960 net operating income (NOI).
If you managed to increase sales volume by 50 percent to 9,360 (6,240 * 1.5) or 30 cars a day and achieve the benchmark average price of $7.50, gross becomes $70,200 less variable unit cost equals $51,480 NOI.
Change in NOI is $26,520 (51,480 – 24,960).
Maximum monthly payment = $26,520 / 12 / 1.25 = $1,768
$1,768 implies you could afford to lease about $88,000 worth of machinery from the improvement in NOI without affecting the margin available to cover fixed cost and leave a profit.
Personally, I would have some comfort if anticipated sales were 40 or 50 cars a day.