Firstly you must register for VAT with HM Revenue and Customs (HMRC) if your business’ VAT TAXABLE turnover is more than £85,000.
Residential lettings are exempt from VAT, so NOT included in the taxable turnover. Genuine disbursements are outside the scope of VAT hence also not in the taxable turnover number. Hence the only number that matters is the £50k which is less than £85k hence no obligation to register.
However you may want to register voluntarily if the customers are in business, so that you recover input tax subject to partial exemption rules. Note expenses recharged to customers are not disbursements, and so count towards taxable turnover.