I understand the principle of the idea, but also see areas of fundamentally prohibitive conflict with the rule of law, which include, but not limited to these:
Change of use - material change or conversion from existing to new use-class (e.g. munitions depot to hospitality use), as rightly raised by Darko earlier
Unfitness for human habitation - for a property to be deemed unfit for human habitation, one or more of the following must be absent, dysfunctional or unsafe: natural lighting, ventilation, water supply, drainage and sanitation, facilities for preparation and cooking food, facilities for the disposal of waste water, the internal arrangement of furniture and appliances, any other hazards which risk your health or safety
Dangerous premises - properties that aren't properly maintained and compliant with building and safety codes or are otherwise unsafe, also as raised earlier
EU Convention - although not explicitly included in the European Convention on Human Rights (ECHR), the right to adequate housing is enshrined in numerous concrete legal norms, namely Article 2 (right to life), Article 3 (prohibition of torture or inhuman or degrading treatment), Article 6 (right to a fair trial), Article 8 (right to respect for private and family life), Article 13 (right to an effective remedy), Article 14 (prohibition of discrimination), Article 1 Protocol 1 (protection of property)
UN International Law of Right to Adequte Housing - Universal Declaration of Human Rights on right to a standard of living adequate for health and wellbeing (article 25(1)) and International Covenant on Economic, Social and Cultural Rights (article 11(1)). These pieces of international law impose legal obligations on states parties
In addition, other key considerations include:
Historical background that led to the state of dereliction, which may render the venture unviable or add value to it
Conservation of local or world heritage - like historical background, this may affect the viability of the project negatively or positively
The aim of setting out these critial issues is simply to focus the mind on the practical legal realities of the real world right from the outset. Some platforms, to their detriment, have chosen to ignore how the real world oprates to provide technology-enabled traditional services and call themselves "technology companies", in a futile attempt to hide under the veil of internet neutrality. Sooner or later the slow grinding mechinery of the realworld legal system will catch up, as Uber and others have come to realise.
These conflicts MUST safely be removed to pave the way for an entirely new highly viable "squatting-inspired" ultra-low-cost hospitality sector, which is targeted at the back-packing traveller/adventurer.
There will be upfront capital costs to renovate the properties to the intended standards. The finished properties will be structurally sound and well-insulated with the charm of restrained character - worn ceiling, wall and door/frame finishes, old fittings, polished concrete or stripped wooden floors, warm, clean and comfortable, etc. Sanitary and cooking amenities are modern, but with old/period fittings (ideally, salvaged) to reflect property period and enhance the "squatting" experience.
Regardless of any local poor standards, all properties will be renovated to international quality, but with local character.
Assume that the head image shows an acquired property undergoing renovation before operation.
The platform is a free-memebership website with network effect and possibly e-commerce (shop; ad, promo and sponso publishing).
These may be offered as shelter only (minimal or no room furniture) or shelter-and-breakfast at ultra-low-costs and marketed with local attractions. Guests bring their own back packs or collect on arrival.
Properties may be leased to the platform for a certain term, in which case, the platform takes full responsibility for management and maintenance (e.g OYO). An alternative arrangement may allow the host/owner to take full property-side responsibility for hosting, management and maintenance (e.g. AirBnB) or involve a combination of both options.
The platform will earn commission or retain full rate paid, depending on arrangements with the property owner.
Members may be encouraged by way of special offers, etc to find potential suitable properties in their local areas and possibly become ambassadors for the properties, if successfully acquired by the platform and operational.
Once established, partnerships with budget airlines and other compatible operators will help the platform scale and enhance its unique selling point (USP).
"Squatting for free vs. paying"
Both could be achieved seamlessly, if the platform unlocks the hidden value of "squatting" as a means of adventure and lifestyle (normadic).
Squatting involves wider complex social issues that relate to homelessness and should seriously be considered in the round. Generally, people who squat are forced to do so, due to personal circumstances and not in a position to afford paying rent for the squat; albeit trashing the very property that gives shelter will be viewed by any reasonable/responsible "squatter" as senseless and inexcusable.
Nevertheless, if this is an area of interest for the platform, it could operate as a social enterprise with commercial and non-commercial activities to provide a wider positive social impact. This means that some properties leased to the platform could be made accessible to the homeless for free or social rent in relation to those entitled to state benefits; in short, depending on personal circumstances.
It is also a good way to partner with local authorities to secure property supply and benefit payments. The platform could lease empty derelict flats from local authorities on a peppercorn-rent basis, for reviewable fixed terms. It will then refurbish the properties minimally, for both commercial short-stay and non-commercial temporary accommodation.
A squatting-inspired online platform without any conflict with the rule of law is highly viable. It should certainly be pursued with a well-defined business plan. Source funding, develop website and start with one suitable local realsite, as a route to market.