I want to determine if the business I'm buying is worth it and I'm paying right price?

What you must consider is that you are BUYING a JOB...

To Over simplify...

How much does this JOB pay YOU per Year after all your expenses (and the extra self employment taxes).

There is a difference between buying a job that pays $20,000 per year and a job that pays YOU $95,000 per year.

1. First calculate How much SPENDABLE money the Route is going to have left for you after all expenses and taxes.
2. You must KNOW how much YOU could earn doing the same amount of work for someone else as employee.
3. You must calculate the COST to you of comming up with the $150,000 to purchase this JOB (route). (if you have the $150K, what is the best rate of return you can get on it investing it somewhere else?). .(If you don't have it, what interest rate will it cost to borrow it)?
4. Find our how much interest you would either lose by not investing or PAY to get the money per year.
5. if you have health insurance now, how much will it cost to get health insurance when you are self employed? anualize the difference between what you are paying now and what you will pay.
There are many other factors, but lets run with these..

Lets say you can earn $40,000 working for someone else.
BUT, you health insurance is gonna cost $3000 more per year.
AND you borrow ALL of the $150,000 at 9% interest.
The COST of the money is then $13,500 per year.

So a simple cost of the JOB is $56,500 per Year...

If you cant take a Lot more out of the JOB then THAT Every year from the Profits, then you can not afford to quit the other job.

NOW, lets work backwards...

If you have 200 accounts that pay $120 per month 7 months out of the year that is $168,000 GROSS (not net) that you start subtracting your expenses from.

Expenses might be GASOLINE at $3 per gallon times 1 gallon per week per client times 30 weeks = $18,000 in gas per year for equipment.
If your average drive to a client is only 5 miles, your Truck fueld could be an additional $6000 per year plus you are putting 30,000 per year on an already old truck. (assume 15 miles per gallon).

The govt assumes driving such a vehicle will cost you 45 cents per mile including fuel, so be prepared to pony up an additional $7,500 for upkeep on the vehicles.

Some people are going to STIFF you and not pay, so you either have to write those off or pay for collections.
Assume 5 percent loss on that for $8,400

Your equipment is Going to Break and you will need to replace it or repair it. allow at Least $9,000 per year to do that perhaps much more.

If you have 200 clients to service per week, that is 33 per day 6 days a week. You could not possibly do that all by youself.
You will have to have 4 people helping you 9 hours per day.
Even if you only pay them $9 per hour that is $1,620 per week or $48,600 per year. add an additional 9 percent for FICA and MED
and you are at $53,000 or so.
Lets just see where we are so far

Gross earnings $168,000
Gasoline $ 18,000
Truck Fuel $ 6,000
Vehicle upkeep $ 7,500
Bad debt and collections $ 8,400
Labor and Payroll Taxes $ 53,000
EQ Repairs and upkeep $ 9,000
Business Insurance costs$ 6,000
Advertising to keep cust $5,000

So far you expenses are 106,900 per year
and there will be many more.

Subtracted from 168,000 and there is only $61,100 left to pay ALL the rest of the Bills you have for the year like:
Telephone, paper goods, banks fees, credit card fees, Rent on a place to store everything, Permits, licenses, Business Taxes, furniture, signage, medical bills, extra clothing and shoes, and a whole lot of etcetera.

If you ONLY have $5,000 more in expenses in this example, then it would be better to keep your $150,000 and invest it and keep your other job.