Hi, before buying the business, ask yourself these questions:
1. How long has your friend been servicing the 80 customers?
2. How often are they serviced?
3. What is the weekly/monthly turnover?
4. How much is your friend asking for the business?
5. Is he willing to introduce you to the customers, and as you have no previous experience, can he give you some training in how to operate the equipment?
Satisfy yourself that the answers check out and get proof of accounts, record of dates cleaned, and that the customers have been paying on time.
If all the above checks out, then you may have the basis for a business, but, depending on the turnover figures and how much you need to be earning, there will likely still be a lot of work to find via canvassing, leaflets or whatever your preferred method of procuring more customers is before it makes you a decent living.
If you are prepared to work hard, and are determined to keep going even when it gets tough, there is every possibility you can succeed.
Best wishes and welcome to the forum.
John