50/50 split, sold on contract with interest, split?

[Ira Wayne]

I am an investor, decided to go in 50/50 whereas I pay for 100% property and materials. My friend does 100% of work, which he ended up doing about 80% of work. The house sat on market until sold on contract where the past 5 years I have collected 6% monthly interest on a house sold for $120k. Just recently sold the home outright with friend not being paid a dime yet, upon his request. Lets say profit for the sell of the home was 30k, 15k a piece at a 50/50 split. If I collected lets say $800 a month on each mortgage payment, $500 of that being interest on average from owners for 5 years, who is entitled to the total sum of interest? Should it be split at (12x5)x500) / 2 ? Or am I entitled to a higher percentage of interest collected since I assumed 100% of risk?