Guaranteed Payments to a partner have to be spelled out in the partnership agreement. Then when you write the check for the guaranteed payment you use the guaranteed payment expense account you create in the chart of accounts. A audit, without that specification in the partnership agreement will cause that expense to be disallowed and that is a problem for all partners when you have to do an amended partnership return and so do the partners.

Partners are not vendors, make them inactive

Partners, when the partnership is formed, bring cash and maybe assets and sometimes receivables as part of their starting equity.  once that happens in forming the partnership, it is no longer a personal thing, it belongs to the partnership

The partnership is a business, it is not 3 people acting individually. Expenses are paid from business funds, no matter who does the actual buying, or who uses the supplies.

The partnership charges the customer and that amount is income to the partnership.

At the end of the year you complete the tax form 1065 and as part of that a form K-1 is generated per partner. That K-1 provides information on the partners share of income and expense per the partnership agreement on profit (loss) sharing.

During the year a partner can take a draw on equity. You write the check and use that partners equity drawing account as the expense for the check.

A good partnership agreement, IMO, will state a minimum balance required per partner equity account, and often require the total draws per year to not exceed last years retained earnings distribution or some percentage thereof.

For a company taxed as a sole proprietor (schedule C) or partnership (form 1065), I recommend you have the following for owner/partner equity accounts (one set for each partner if a partnership)
[name] Equity (do not post to this account it is a summing account)
>> Equity
>> Equity Drawing - you record value you take from the business here
>> Equity Investment - record value you put into the business here