How does sales commission for selling services work?

[sales]

Hi,
M friend's husband wants me to help him sell a service he's developed for companies. It's basically signing up to a software based service he's developed that would be very useful for certain types of companies. I won't give too many details so it can't be identified. But first of all he wanted me to do the sales and marketing. Basically visiting companies demonstrating what the software can do for them then getting them to sign up for the service. Once they sign up they will pay him a monthly fee. I am happy to do this as I think the service is a great idea and companies will go for it, so I won't feel like I'm trying to sell a complete lemon. In fact we've tentatively approached a few companies and had very good response and two are already signing up out of four approached.
They would pay about a monthly fee of £50, but I think we may adjust that fee depending on how big the company is. The fee is also per branch, so I may approach one office and get 50 branches signed up from just one meeting.
I firstly thought I'd like shares on the company to do this work as I'd love to get in on it as I think it'll be big, but he's not keen on doing that and wants to offer me commission on sales.
My question is: what should I ask for, for example if I have a meeting with a company manager and from that I get that company (with 60 branches signed up all for £50 per month per branch) I guess I get 10 or 20 % of that figure, but for how long? Do I get 10 or 20 % of the monthly fee for as long as that company stays signed on with him? What if I just get 6 companies onboard then feel I can't work with the guy and don't carry on or he dumps me. Do I them carry on getting that 10 or 20 % because of course without me making that initial sale he wouldn't then be getting that money in each month.
I mean for selling a product it's straightforward you sell 10 vacuums then leave the company, you walk away with your 10 % of the vacuums sale price or whatever. But in a business where the money will keep coming in, in the way of a monthly fee, how does it work.
I can lead him as to how it is to be structured as he hasn't a clue either how it works.
Advice please!

Sales, I work for a large listed company and we have a software division.

When we make a sale to a company, we would normally have an annual contract with them (or possibly multi-year deals eg 2 or 3 years). We then renew this annual contract on its anniversary. A salesperson would be paid a commission for sealing the deal, regardless of whether the customer has paid yet. However, we are a large company with lots of cash to spare! When the contract is renewed, whichever salesperson agrees the renewal with the customer would get the commission, but at a lower rate than the original contract as it is easier to renew a contract than to obtain a new customer. If one of our salespeople left the company, they would not continue to receive commisson, but this is due to our terms and conditons of employment and need not necessarily be the case.

You will find that your customer will not want to sign deals with no end date, they would be for a finite period of time (probably). I think you ought to be agreeing a set % of each new deal to be paid on signature of contract, and then a monthly amount to be paid to you each time the customer pays, to the end of the customers first year. For example if 1st year is worth £600 and you want 15% commisson, (£90 in total) you should ask for some of this at the start and the rest spread over the year (perhaps £30 upfront and £60 spread-to be negotiated with the business owner). If you happen to be the salesperson that then renews that deal, you would receive commission in year 2 as well and so on. You should make sure that your terms state that you will continue to receive this commission to the end of the customers contract, even if you were to leave. He may not agree to this but worth a try.

Does that all make sense?

Yes yes makes sense! Is it totally unusual to just have commission only as your pay, no actual salary?

If you are self-employed this would be pretty normal to be commission only.

If you are an employee then it would be unusual, you would have a basic salary plus commission (at least national minimum wage).