The problem with absolute rights of free contract is not only that it leaves people free to diminish themself into servitude, it makes it possible (in fact likely) that the powerful will use the ability of people to do that to their advantage. In the United States, as in most common law systems, there are significant barriers to pure/broad forms of philosophical free contract - these exist both in the general sense (e.g. no selling of one's self to slavery) and particularly in issues relating to essentials - the law recognises that contracts happen in the context of real circumstances in society and that protections are warranted. We regard absolute (or overly strong) rights to contact as contrary to the public good - they both allow a race-to-the-bottom of indebtedness of workers (a person who cannot sell themself into servitude, pressed to the wall, will find other means to support themself, often by making society correct whatever situation led to it) and deny the collectivity of societal bargaining in the process of lawmaking. Society, embodied in the state, is entitled to regulate legal institutions (which contracts are) and societal behaviour in order to serve the public good - this is the sole purpose of government. It is undesirable that society allow one set of parties to grossly benefit at the expense of another, particularly (but not only) when the relevant acts threaten the basic needs, ability to be a citizen-in-good-standing, and solvency of the weaker parties. In all nations, there is not an absolute right to free contract - there are limitations based on the content of the contract depending on its specifics and the legal status of those contracting. In some nations, institutions such as allodial title (unseizable by bankruptcy, often not taxed, and not mortgagable) acted to protect the holder. Limits such as these may limit the ability of people to leverage themselves and their essentials, but in many cases the ability to do so is a danger to them.
In capitalist or transitional societies, we hold that contracts not be free - that there both be numerous specific protections based on the type of contract and the status of the contractor (which is the case in the United States and many other nations) as well as preferred contracts designed for equitability (particularly focusing on other things than basic rates, e.g. arbitration, adjustments, cancellation) given preference both by potential tax breaks and promotion by the state.
In socialist societies, we hold that contracts will play a significantly smaller role in societal institutions, as the distinction between the public and the provate sector will be redrawn and people will be less vulnerable to circumstances where their needs, standing, and solvency would be denied. In all societies, we hold that property is a privilege, given because of need or service to society, and held on privision that doing so does not go against the public interest. We advocate that personal posessions, particularly reasonable amounts of materials that are not needed for the well-being of another, are to be considered nearly inviolate, that reasonable amounts of real property (such as land), particularly that of personal use, be considered assigned with broad privileges for the long term provided there is not a good public policy reason to transfer it in whole or part to other people or uses, and that means of production be generally considered owned by society as a whole and administered by its institutions rather than individuals except in rare circumstances.
In socialist societies which are a protected republic (meaning where they have philosophers or the party guarding socialist ideals from above meeting democratic structures from below), societal institutions allocated land should generally be governed democratically. In syndicalist, commune-centric, or bund-centric systems, allocated land and resources should be jointly governed by those structures and institutions representing the broader interests of society.