COMMITMENTS AND CONTINGENCIES Legal Proceedings . We are involved in various lawsuits arising in the normal course of business. We believe that such matters will not have a material adverse effect on our consolidated financial statements. Environmental Matters . It is generally our policy to obtain a Phase I environmental assessment of each property that we seek to acquire. Such assessments have not revealed, nor are we aware of, any environmental liabilities that we believe would have a material adverse effect on our financial position or results of operations. We own properties that contain or potentially contain (based on the age of the property) asbestos or lead. For certain of these properties, we estimated the fair value of the conditional asset retirement obligation and chose not to book a liability because the amounts involved were immaterial. With respect to certain other properties, we have not recorded any related asset retirement obligation as the fair value of the liability cannot be reasonably estimated due to insufficient information. We believe we do not have sufficient information to estimate the fair value of the asset retirement obligations for these properties because a settlement date or range of potential settlement dates has not been specified by others and, additionally, there are currently no plans or expectation of plans to demolish these properties or to undertake major renovations that would require removal of the asbestos, lead and/or underground storage tanks. These properties are expected to be maintained by repairs and maintenance activities that would not involve the removal of the asbestos, lead and/or underground storage tanks. Also, a need for renovations caused by resident changes, technology changes or other factors has not been identified. Insurance. We carry insurance coverage on our properties in amounts and types that we believe are customarily obtained by owners of similar properties and are sufficient to achieve our risk management objectives. Restrictions on Taxable Dispositions. Approximately 24 of our properties, consisting of approximately 4,099 apartment homes, are subject to restrictions on taxable dispositions under agreements entered into with some of the sellers or contributors of the properties. The real estate investment amount of these properties, net of accumulated depreciation, was approximately $532.0 million at December 31, 2018. The restrictions on taxable dispositions are effective for varying periods. We do not believe that the agreements materially affect the conduct of our business or our decisions whether to dispose of restricted properties during the restriction period because we generally hold these and our other properties for investment purposes rather than for sale. In addition, where we deem it to be in our shareholders best interests to dispose of such properties, we generally seek to structure sales of such properties as tax deferred transactions under Section 1031 of the Internal Revenue Code. Otherwise, we may be required to provide tax indemnification payments to the parties to these agreements. Redemption Value of Units . Pursuant to a Unitholders exercise of its Exchange Rights, we have the right, in our sole discretion, to acquire such Units by either making a cash payment or acquiring the Units for our common shares, on a one -for-one basis. All Units receive the same per Unit cash distributions as the per share dividends paid on common shares. Units are redeemable for an amount of cash per Unit equal to the average of the daily market price of our common shares for the ten consecutive trading days immediately preceding the date of valuation of the Unit. As of December 31, 2018, April 30, 2018 , and April 30, 2017 , the aggregate redemption value of the then-outstanding Units owned by limited partners, as determined by the ten -day average market price for our common shares, was approximately $68.4 million , $74.7 million , and $95.1 million , respectively. Joint Venture Buy/Sell Options. Several of our joint venture agreements contain buy/sell options in which each party under certain circumstances has the option to acquire the interest of the other party, but do not generally require that we buy our partners interests. However, from time to time, we have entered into joint venture agreements which contain options compelling us to acquire the interest of the other parties. We currently have one such joint venture, which owns Commons and Landing at Southgate in Minot, North Dakota, in which our joint venture partner can, for the four -year period from February 6, 2016 through February 5, 2020, compel us to acquire the partners interest for a price to be determined in accordance with the provisions of the joint venture agreement. The joint venture partners interest is reflected as a redeemable noncontrolling interest on the Consolidated Balance Sheets.