Thank you for this all important question about the initial cost of going solar especially. Personally I think this is where your business strategy and unique business model will come into play. Before I say more on that, first of all you will have to:
1. Prove to your client in concrete terms how solar is actually cheaper than other fosil fuel alternatives in long run.
2. Show your client other benefits and cost saving merits of clean energy over other sources. For example, you can not really measure the value in monetary terms of the noise and air pollution that diesel generator produces.
As for your question, like I said, this is where your business model comes in. Essentially, How do you want to reduce the initial cost for your client?

1. You may provide financing options for your client. For example, you can spread the payment and have them pay an initial deposit and spread the rest over a period of time. This way, the burden of the cost is easier on the customer.
2. Drastically reduce your customer load and provide a smaller system at a lower rate for her. This is where energy efficiency comes in. For example, as an installer, you will have to be able to able to advice your client accordingly. You may have to replace his 100W incandescent yellow bulb with a 9W LED bulb and save up to 90% of power. Same applies to other house hold appliances.
3. Then the last option is your unique business model. Think about this problem and you may come up with a big break in this challange.

Thank you, I appreciate your insightful response.