the problem with 2018, unless you extended the return to 10/15/2019 it is now too late to amend. you only have 3 years from the original due date 4/15/2019 or a properly extended due date of 10/15/2019
let's ASSUME you did extend so you can amend
storage fees for a personal account are not tax-deductible.
interest would be investment interest and be reported on for 4952, to be of benefit you must be able to itemize. only the amount paid in the year paid is deductible for that year and limited to investment income.
did you buy $75k paying cash of $50K and a note for the other $25K
or did you buy $50K paying cash of $25K and the note for $25K
let's say you paid $25K cash and took out a note for the other $25K. Your tax basis would be $50K
you sold 70% of the $50K in 2018 for X all of which went to satisfy the note. so your cost basis would be $35K and the proceeds X was the cash received on liquidation - the sales price.
you sold 30% of the $50K in 2019 for Y all of it went to satisfy the note, so your cost basis is $15K and sales price is Y
