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HP 20S and HP 21S: Qualifying Loan Amount (28:36 ratio)

HP 20S and HP 21S:  Qualifying Loan Amount (28:36 ratio)

Introduction

The program presented in today’s blog entry will calculate the qualifying loan amount given the following:

*  Loan’s annual interest rate and term (in years)
*  The borrower’s monthly gross income
*  The borrower’s monthly non-property related debt (credit cards, auto loans, store bought appliances on credit, etc).  Do not include utilities or phone bills.
*  The estimated monthly property tax and insurance.  For this program, combine the two amounts.

Before running the program, store the following amounts in the following registers:

R0:  Monthly Income
R1:  Monthly Debt
R2:  Monthly Property Taxes and Insurance
R3:  Annual Interest Rate
R4:  Term

The down payment is not taken into consideration.

The result is the loan amount using the standard 28:36 ratio (stored in register R5).  The 28:36 ratio is the guideline that the borrower spends no more than 28% of their income on housing expenses, and no more than 36% of their income on all debt service.

HP 20S and HP 21S Program:  Qualifying Loan Amount

The key codes for most steps are the same.  Lines where the key codes are different are noted, particularly the percentage function.

STEP  KEY      KEY CODE
01    LBL E    61, 41, E
02    FIX 2    51, 33, 2
03    RCL 0    22, 0
04    ×        55
05    3        3
06    6        6
07    %        HP 20S: 51,14  HP 21S: 51, 53
08    =        74
09    –        65
10    RCL 1    22, 1
11    =        74
12    STO 6    21, 6
13    RCL 0    22, 0
14    ×        55
15    2        2
16    8        8
17    %        HP 20S: 51,14  HP 21S: 51, 53
18    =        74
19    STO 7    21, 7
20    RCL 6    22, 6
21    INPUT    31
22    RCL 7    22, 7
23    X≤Y?     61, 42
24    SWAP     51, 31
25    STO 8    21, 8
26    RCL 2    22, 2
27    STO – 8  21, 65, 8
28    1        1
29    –        65
30    (        33
31    1        1
32    +        75
33    RCL 3    22, 3
34    ÷        45
35    1        1
36    2        2
37    0        0
38    0        0
39    )        34
40    Y^X      14
41    (        33
42    1        1
43    2        2
44    +/-      32
45    ×        55
46    RCL 4    22, 4
47    )        34
48    =        74
49    ÷        45
50    (        33
51    RCL 3    22, 3
52    ÷        45
53    1        1
54    2        2
55    0        0
56    0        0
57    )        34
58    =        74
59    ×        55
60    RCL 8    22, 8
61    =        74
62    STO 5    21, 5
63    RTN      61, 26

Example

R0:  Monthly Income = $4,485.00
R1:  Monthly Debt = $375.00
R2:  Monthly Property Taxes and Insurance = $126.83
R3:  Annual Interest Rate = 5%
R4:  Term = 30 years

Result:  $207,288.60

Eddie

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