Thanks for your question - I am Sam and I am one of the UK tax experts here on Just Answer.
I am afraid being self employed or employed is not a matter of choice but a matter of law, and under the employment status legislation - I cannot possible see how this could be self employment (which it would have to be for you to either be a sole trader or limited company becase if you would be an employee were ir not for the li8mited company then this breaches IR35 legislation also )
Your employment is just that - subject to tax and National Insurance under PAYE
Your rental income is just that - subject to Schedule A taxation (so tax and no National Insurance)
This new venture is one of employee unless you set up on your own sourcing clients through advertising, have your own business premises, admin costs and overheads and charge your clients a fee directly.
It sounds like this business is operating out of the scope of tax law, which will affect your rights and tax position, see link here re employment status
and read through each of the tabs. Then complete the Q & A tool - employment status indicator for a formal view from HMRC http://tools.hmrc.gov.uk/esi/screen/ESI/en-GB/summary?user=guest
There might be scope if you work from home, use your own business equipment and charge for the hours worked, and will provide these services to many estate agents - but not if its just a one on one situation.
Have a read through the legislation and try out the tool - if you have any follow up questions, then please do ask.