I assume you mean real estate developing or some kind of property development whether it be commercial or residential.
Either way, in order to sell any business there has to be value in it. Generally, the value of a business would be not much more than the value of its assets less outstanding liabilities, or its net worth. In order to get more than that the business would have to have demonstrated profitability and be sold as an operational enterprise, fully functioning.
In order to sell a business as a fully functioning, operational entity, you would probably have to go to its major competition or a larger business in the same line of work and offer them a good price for it. To sell it for the value of its assets would be done at auction.
Finding an investor would be a matter of seeking venture capital. There are many venture capital firms that would entertain an application for financing in exchange for an ownership interest in the company but they would need to be convinced that a healthy return on their investment can be realized.