How does Papers, Please decide when to offer better apartments?

Question

During the course of Story mode on Papers, Please, different apartment classes are offered at different stages within the game. Apartments don't serve any monetary advantage, and are only there to create some realism in the game, with only an achievement as a reward for upgrading apartments to the fullest extent.

There is already documented knowledge of the earliest days each class of apartment can become available:

• The inspector begins the game in a class-8 apartment.
• Class-7 becomes available no earlier than on day 12.
• Class-6 becomes available no earlier than on day 17.
• Class-5 becomes available no earlier than on day 22.

However, depending on your current amount of money and previous decisions, sometimes new apartments aren't offered to you at the earliest they become available. Everything I have read only states that new apartments become available “occasionally,” but don't elaborate on what the exact conditions are to be offered another apartment.

What are the exact criteria that are checked to decide whether to offer another apartment class?
Hence, what is the most important factor to consider for one to ensure they are offered a new apartment at the earliest possible opportunity?

Answer 1

The game has a list of NightEvents, each with a tree of requirements and operations. Here's a representation of the tree for the APARTMENT_UPGRADE event, which seems to trigger at the start of every night from night 12 onwards:

RUNSTEPS ? Night/Savings < 20
    RUNSTEPS ? Night/Apartment == C7
        SAY A cheaper class 8 apartment is available. (Rent = 25, Heat = 10)
        RUNSTEPS MOVE TO CLASS-8 | 75 | NO
            RUNSTEPS YES
                SETFACT Night/Apartment C8
                SETFACT Night/Rent -25
                SETFACT Night/Heat -10
                SETFACT Night/ApartmentTimer 4
    RUNSTEPS ? Night/Apartment == C6
        SAY A cheaper class 8 apartment is available. (Rent = 25, Heat = 10)
        RUNSTEPS MOVE TO CLASS-8 | 150 | NO
            RUNSTEPS YES
                SETFACT Night/Apartment C8
                SETFACT Night/Rent -25
                SETFACT Night/Heat -10
                SETFACT Night/ApartmentTimer 4
    RUNSTEPS ? Night/Apartment == C5
        SAY A cheaper class 8 apartment is available. (Rent = 25, Heat = 10)
        RUNSTEPS MOVE TO CLASS-8 | 225 | NO
            RUNSTEPS YES
                SETFACT Night/Apartment C8
                SETFACT Night/Rent -25
                SETFACT Night/Heat -10
                SETFACT Night/ApartmentTimer 4
RUNSTEPS ? Night/Savings > 20
    SETFACT Night/ApartmentTimer --1
    RUNSTEPS ? Night/ApartmentTimer <= 0
        RUNSTEPS ? Night/Apartment == C8
            SAY A class-7 apartment is available. (Rent = 30, Heat = 10)
            RUNSTEPS MOVE TO CLASS-7 | -100 | NO
                RUNSTEPS YES
                    SETFACT Night/Apartment C7
                    SETFACT Night/Rent -30
                    SETFACT Night/Heat -10
                    SETFACT Night/ApartmentTimer 5
                RUNSTEPS NO
                    SETFACT Night/ApartmentTimer 2
        RUNSTEPS ? Night/Apartment == C7
            SAY A class-6 apartment is available. (Rent = 40, Heat = 5)
            RUNSTEPS MOVE TO CLASS-6 | -100 | NO
                RUNSTEPS YES
                    SETFACT Night/Apartment C6
                    SETFACT Night/Rent -40
                    SETFACT Night/Heat -5
                    SETFACT Night/ApartmentTimer 5
                RUNSTEPS NO
                    SETFACT Night/ApartmentTimer 2
        RUNSTEPS ? Night/Apartment == C6
            SAY A class-5 apartment is available. (Rent = 50, Heat = 0)
            SAY Class-5 is the best a worker can have.
            RUNSTEPS MOVE TO CLASS-5 | -100 | NO
                RUNSTEPS YES
                    SETFACT Night/Apartment C5
                    SETFACT Night/Rent -50
                    SETFACT Night/Heat 0
                    ENABLE Achievement ACH_APT_CLASS5

It seems that the game has a hidden counter that decreases by 1 each night if you have more than 20 credits for the night's opening balance (savings). Each night that opens with more than 20 credits in savings will progress you one step to being offered an apartment upgrade, which will occur when the counter reaches 0. If an upgrade is accepted, the counter resets to 5, and if declined, resets to 2.

Likewise, nights opening with fewer than 20 credits in savings will offer you the option to downgrade to class-8 if you have upgraded from class-8 in the past. Unlike upgrades, downgrades do not have a counter and will be offered any time your savings match this criterion. Should a downgrade be accepted, the upgrade counter resets to 4, no matter what progress you had previously.

The fact that this counter resets to 5 upon an accepted upgrade is supported by the previously-known info of upgrades, as the earliest possible upgrades to classes 7, 6, and 5 are each five days apart.

In conclusion, the best way to ensure you get each apartment upgrade offered as soon as possible is to end every day with at least 20 credits in savings; I would recommend leaving a safe margin of about 5 credits by aiming for 25 credits.

Answer 2

Don't know the exact criteria but according to Papers, Please Wiki:

• Class-8 – This is the initial apartment provided to the inspector and his family at the beginning of the game.
• Class-7 – Available at the end of day 12 at the earliest.
• Class-6 – Available at the end of day 17 at the earliest, if already living in a class-7 apartment.
• Class-5 – Available at the end of day 22 at the earliest, if already living in a class-6 apartment.

Also, according to this Papers, Please Wiki discussion thread there might be faster ways, but for now, this is the earliest proved.