Lube shop

I currently pay $2.49 a qt for conventional motor oil. that's bulk pricing. that price also pays for my tanks and other equipment.
I buy oil filters from Mighty. Most of my filters run $1.69 ea. The most I pay for a filter is $9.99 and that's for diesels.
The nice thing about Mighty is they also sell other filters. they also carry other parts and have a nice consignment plan.
one thing you will need to take into consideration is the different types of oil you'll need to stock, ie conventional, synthetic and the grades. You'll also have customers who want OE filters, so keep that in mind also.
You will never make money on $9.99 or even $19.99 oil changes unless your able to upsell other services. That's where BG products come in handy. Good product, does what its supposed to do and cheap enough to make money off of.
Good news! disposal of oil is a money maker. I get $1.10 a gallon for waste oil. That has coolant and everything mixed in. The EPA is a huge P.I.A. about tanks.
You need to sit down and figure expense vs. income. working for nothing sucks!