PORTLAND — A letter of intent between the Port of Portland and a group seeking to build a Major League Baseball-caliber stadium calls for the private group to pay up to $1.5 million over two years to exclusively negotiate redevelopment of a waterfront site. The group would then pay the Port at least $900,000 a year as they build out the property, according to terms spelled out in the letter.The Port signed off on the letter Nov. 28. The Portland Diamond Project, which is seeking to lure an MLB team to Portland, agreed the next day. The group released artist renderings of a new baseball stadium at the Port’s 45-acre Terminal 2 marine cargo site the same day.The terms of the agreement hadn’t been publicly released since the proposed site announcement. A copy of the letter of intent and its attachments were obtained by The Oregonian/OregonLive through a public records request.Both sides have carried out due diligence since then. They have up to six months to inspect the property and complete any other feasibility analysis they feel is necessary, the letter said.During this period, the Diamond Project is required to inform the Port of plans related to the proposed venture, including the group’s ownership structure and other financial information that explains how it will be able to execute the deal. They’ll move to exclusive negotiations afterward, during which the project plans to pay $375,000 during the first quarter, $125,000 for the next three quarters after that and $187,500 each quarter over the next year, if necessary.