HP 12C and HP Prime:
Combo Loans
Introduction
Home buyers with good credit are sometimes offered a combo
loan, also known as a “Piggyback” loan, as a financing option in purchasing the
house. When more than the amount of a
purchase of a home is above 80% of the purchase price, private mortgage
insurance (PMI) is required. In order to
save money, combo loans split the price into multiple loans. Common types include:
80:20: Two loans, one
for 80% of the price (large), 20% of the price (small)
80:15:5: Two loans,
one for 80% of the price (large), 15% of the price (small), with 5% of the
price as a down payment
80:10:10: Two loans,
one for 80% of the price (large), 10% of the price (small), with 10% of the
price as a down payment
Each loans have separate terms (number of years and interest
rate). Monthly endofperiod payments
are assumed.
HP Prime Program
COMBOLOAN
The program COMBOLOAN calculates the payments for both
separate loans and combined loans. This
particular loan covers of three types:
80:20, 80:15:5, and 80:10:10.
EXPORT COMBOLOAN()
BEGIN
// EWS 20180405
// Piggyback Loan
LOCAL a,lst,k;
LOCAL t1,t2,i1,i2;
LOCAL d,p1,p2,p;
// terms, order allows to
// use eqn −5*k+25
lst:={"80:20","80:15:5","80:10:10"};
// input
INPUT({a,t1,i1,t2,i2,{k,lst}},
"Payment: Combo Loan",
{"Loan:
","Term1:","Rate1:",
"Term2:","Rate2:","Type
:"},
{"","years","","years","",""});
// calculation
p1:=Finance.TvmPMT(t1*12,i1,a*0.8,0,12);
p2:=Finance.TvmPMT(t2*12,i2,a*(−0.05*k+0.25),0,12);
p:=p1+p2;
// down payment
d:=−a*0.05*(k1);
// payment: down, total,
// large, small
RETURN {d,p,p1,p2};
END;
Output: {down
payment, total payment, large payment, small payment}
Examples:
Loan Amount:
$200,000.00
80% Loan: Term: 30
years, Rate: 4.5%
Small Loan: Term: 15 years, Rate 5%
Example 1: Type 80:20
Result: {0,
1,127.01, 810.70, 316.32}
Example 2: Type
80:15:5
Result: {10,000.00, 1047.93, 810.70, 237.24}
Example 3: Type
80:10:10
Result: {20,000.00,
968.86, 810.70, 158.16}
HP 12C Platinum
Program: 80:10:10 Combo Loan
Inputs:
Store Loan Amount in R1
Large Loan (80%):
Number of Years in R2, Annual Interest Rate in R3
Small Loan (10%):
Number of Years in R4, Annual Interest Rate in R5
Output:
Large Loan Payment, Small Loan Payment, Combined Payment
(R6)
STEP

CODE

KEY

NOTES

001

42, 34

Clear FIN


002

45, 1

RCL 1


003

8

8


004

0

0


005

25

%


006

13

PV


007

45, 3

RCL 3


008

43, 12

[ g ] [ i ] (12÷)

Store monthly
interest rate

009

45, 2

RCL 2


010

43, 11

[ g ] [ n ] (12x)

Store monthly
payments

011

14

PMT

Calculate payment
of 80% loan

012

44, 6

STO 6


013

31

R/S


014

45, 1

RCL 1


015

1

1


016

0

0


017

25

%


018

13

ENTER


019

45, 5

RCL 5


020

43, 12

[ g ] [ i ] (12÷)


021

45, 4

RCL 4


022

43, 11

[ g ] [ n ] (12x)


023

14

PMT

Calculate payment
on the 10% loan

024

31

R/S


025

45, 6

RCL 6


026

40

+


027

44, 6

STO 6


028

43, 33, 000

GTO 000

On the regular HP
12C, the line is GTO 00

Example:
Terms: 80:10:10
Loan Amount: $200,000.00
80% Loan: Term: 30
years, Rate: 4.5%
10% Loan: Term: 15 years, Rate 5%
Results:
810.70 (payment of
80% loan)
158.16 (payment of
10% loan)
968.86 (payment of
combined loan)
Sources
Calculated Industries Real Estate Master IIIX: Resident
Real Estate Finance Calculator Pocket Reference Guide Calculated Industries, LLC.: Carson City, NV 2010
MortgageInfo.com
“Piggy Back Mortgage Calculator” Mortgage Info.com 2011 http://www.mortgageinfo.com/mortgagecalculators/piggybackmortgagecalculator.aspx Accessed April 4, 2018.
Eddie
All original content copyright, © 20112018. Edward Shore. Unauthorized use and/or unauthorized
distribution for commercial purposes without express and written permission
from the author is strictly prohibited.
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that full credit is given to the author.
Please contact the author if you have questions.
Nice resources!Thanks for sharing such a great valuable info.Keep posting!!
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