Why Does The Buyer Die Walking Into His Home When He Is The Owner And Has Already Died?

The issue is that when the character dies and respawns, everything inside the character (including the Humanoid) is removed and re-created. When this happens, your variable gets reset. Instead of setting a variable to the Humanoid itself, you can try storing the player's name:

local Button = script.Parent
local debounce = true
local HasAccess = "N/A"

function onTouch(Brick)
    if debounce == true then
    local Player = Brick.Parent
    local Hum = Player:findFirstChild("Humanoid")
    if (Hum ~= nil) then
        local Location = game:GetService('Players'):GetPlayerFromCharacter(Player)
    if Location:WaitForChild("leaderstats").Gold.Value >= 20 then
for i = 1,1 do
         Location:WaitForChild("leaderstats").Gold.Value  =  Location:WaitForChild("leaderstats").Gold.Value - 20
        script.Parent.Parent.Name = Player.Name .. "'s House"
        HasAccess = Player.Name
        local Color1 = BrickColor:Random()
        local Color2 = BrickColor:Random()

        script.Parent.Parent.Wall1.BrickColor = Color1
        script.Parent.Parent.Wall2.BrickColor = Color1
        script.Parent.Parent.Wall3.BrickColor = Color1

        script.Parent.Parent.Floor.BrickColor = Color2
        script.Parent.Parent.Head.BrickColor = Color2
        script.Parent.Parent.Roof.BrickColor = Color2
        script.Parent.CanCollide = false
        script.Parent.Transparency = .62
        debounce = false
                end
            end
        end
    end
end

Button.Touched:connect(onTouch)

function Vip(Brick)
    if script.Parent.Parent.Name ~= "House For Sale - 20 Gold" then
    local Toucher = Brick.Parent
    local Hum = Toucher.Humanoid
    if Hum ~= nil then
        if Toucher.Name == HasAccess then
            Hum.Health = Hum.MaxHealth
        else Hum.Health = 0
            end
        end 
    end
end

Button.Touched:connect(Vip)