To start your real estate business, you will need to invest $1,500-2,000 in start-up costs and $1,500/year or slightly more on-going after the 1st year. This assumes that you do not have any listings and that you are not expending additional marketing funds to sell them.he total monthly on average is roughly $400/mo regardless of the number of closed transactions. Add to that any marketing cost for the homes you’re trying to sale and miscellaneous cost, you’re up to $500/mo.