ROI simulator

ROI.py

####
# INPUT
####

# interest rate
IR = 0.029

# Durable life
# Wood: 22, light steel: 27, heave steel: 34, RC: 47
DL = 27

# Age
A = 2

# Equity Rate
ER = 0.3

# Property Asset
ASSET = 23600

# Buy fee rate
BUY_FEE_RATE = 0.06

# INVESTMENT
INVESTMENT = ASSET * (BUY_FEE_RATE + ER)

# Sell rate
SELL_RATE = 1.0

# Sell fee rate
SELL_FEE_RATE = 0.03

# loan break fee rate
LOAN_BREAK_FEE_RATE = 0.015

# ROA
ROA = 0.058

# Building Price Rate
BPR = 0.3

# Running Cost Rate
RCR = 0.15

# TAX Rate
TAX_RATE = 0.37

# loan months
MONTHS = 360

####
# INPUT END
####

# Pricipal on loan
PRINCIPAL = ASSET * (1 - ER)

# Return On Asset
INCOME = ASSET * ROA
INCOME_DECREATE_RATE = 0.01
RUNNING_COST = INCOME * RCR

# monthly interest
MI = IR / 12.

# Monthly Return On Loan
MROL = PRINCIPAL * (MI * (1+MI) ** MONTHS / ((1+MI) ** MONTHS - 1))

# Return On Loan
ROL = MROL * 12

# Return On Loan Rate
ROLR = ROL / INCOME

# CFROI
# CFROI = CF / ((ER + 0.06) * ASSET)

# Depreciation
# Depreciation years
DY = (A > DL) and int(0.2 * DL) or int(DL - A + A * 0.2)
DEPRECIATION = ASSET * BPR * (1. / DY)

# ROI
# 5 years pricipal left
next_principal = lambda p: p - (MROL - p * MI)

CF_TOTAL = 0
p0 = PRINCIPAL
for y in range(int(MONTHS/12)):
    p = p0
    for i in range(12):
        p = next_principal(p)

    INT = ROL - ( p0 - p)
    p0 = p

    CURRENT_INCOME = INCOME * ((1 - INCOME_DECREATE_RATE) ** y)
    TAXING_INCOME = CURRENT_INCOME - RUNNING_COST - INT - (y > DY and 0.1 or DEPRECIATION)
    print("---- year %d ---" % (y + 1))
    TAX = TAXING_INCOME * TAX_RATE
    CF_TAXED = CURRENT_INCOME - RUNNING_COST - ROL - TAX
    CF_TOTAL += CF_TAXED

    # NAV
    SELL_PROFITS = SELL_RATE * ASSET - (ASSET - (y > DY and DY or y) * DEPRECIATION)
    SELL_TAX = SELL_PROFITS * TAX_RATE
    SELL_FEE = ASSET * SELL_RATE * SELL_FEE_RATE
    LOAN_BREAK_FEE = p0 * LOAN_BREAK_FEE_RATE + 6

    NAV = CF_TOTAL + SELL_RATE * ASSET - SELL_TAX - SELL_FEE - LOAN_BREAK_FEE - ASSET * (BUY_FEE_RATE) - p0
    print("CF_TAXED", CURRENT_INCOME,  RUNNING_COST, ROL, TAX, CF_TAXED)
    print('NAV', NAV, (NAV-INVESTMENT) / INVESTMENT)