Are you looking to fully upgrade your PI? Or simply buy one? I'll help you out.

I have everything needed to upgrade your PI at the cheapest price: 10* Property Broker owner, ELBT stock, Law 2910 

I don't have a set price for my PI upgrades. I want to make sure you get the best deal, while still being fair. I am very transparent, from my company and ELBT stock in total i get the largest discount that is possible in the game which is -19% cost.

Name your price, set up a trade, and after accepting, I'll send the fully upgraded PI back to you.

I have a list of what it costs me here so the price you will see below is where I make absolutely nothing.  What I ask is that you provide the cash that it costs me to make the property plus a tip for me... this can be whatever you are comfortable with / whatever you are able to afford.  

If you need a PI created from scratch:

***Popular*** 4225 Max Upgrades PI --- 1.652b is how much it costs me to buy the PI and upgrade it (276m saved on upgrades, 25m saved on PI since I can buy at 475m)

PI w/ only Vault --- Usually costs 716m, my perks reduce it down to 650.14m (40.85m saved on upgrades, 25m saved on PI since I can buy at 475m)
PI w/ only airstrip --- Usually costs 576m, my perks reduce it down to 537.39m (14.25m saved on upgrades, 25m saved on PI since I can buy at 475m)

PI w/ only Interior upgrades --- Usually costs 750.75m, my perks reduce it down to 678.14m (47.5m saved on upgrades, 25m saved on PI since I can buy at 475m)

PI w/ only yatch --- Usually costs 1,395,750,000, my perks reduce it down to 1,200,640,000b (170m saved on upgrades, 25m saved on PI since I can buy at 475m)
PI w/ vault + airstrip --- Usually costs 790.75m, my perks reduce it down to 710.54m (55.1m saved on upgrades, 25m saved on PI since I can buy 475m)

PI w/ vault + Interior --- Usually costs 965.75m, my perks reduce it down to 852.29m (88.35m saved on upgrades, 25m saved on PI since I can buy 475m)

PI w/ plane + interior --- Usually costs 825.75m, my perks reduce it down to 738.89m (61.75m saved on upgrades, 25m saved on PI since I can buy 475m)

***Popular*** (Cheap for First Time PI owner) 2600 happy PI w/ Plane + Medical --- Usually costs 592.64m, my perks reduce it down to 550.16m (17.48m saved on upgrades, 25m saved on PI since I can buy 475m)
***Popular*** 3725 happy PI w/ all but yatch (plane, vault, medical facility, interior) --- Usually costs 1,033,750,000, my perks reduce it down to 927m (106m saved on upgrades, 25m saved on PI since I can buy 475m)

If you have a PI and just need upgrades see prices below:

***Popular*** ALL UPGRADES, Max PI w/ your own basic PI --- 1.177b is how much it costs me to buy the PI and upgrade it, usually costs 1.453b (276m saved on upgrades)

If you need individual upgrades:
All small upgrades --- Cost me 640k (all upgrades under 1m price)
Interior only --- Costs me 202.5m (47.5m cheaper than it costs you)

Plane only --- Costs me 60.75m (14.25m cheaper than it costs you)

Vault only --- Costs me 174.15m (40.85m cheaper than it costs you)

Vault + Plane --- Costs me 234.9m (55.1m cheaper than it costs you)
Plane + Medical facility --- Costs me 74.52m (17.48m cheaper than it costs you)

Interior + Plane --- Costs me 263.25m (61.75m cheaper than it costs you) 

Interior + Vault --- Costs me 376.65m (88.35m cheaper than it costs you)

Yatch only --- Costs me 725m (170m cheaper than it costs you)

All big upgrades minus yatch (plane, vault, medical, interior) --- Costs me 451.17m (105.83m cheaper than it costs you)

ADD ON FEE: For all small upgrades it costs me 640k to add on, these perks despite being cheap add on the amazing perks of +2% gym gains, and +2% damage as well as extra happiness.  If you want these add in an extra 640k.

Shoutout to mug, as always, for being the best founding forefather and for the detailed price breakdown.