It depends on your family, but in my case, we're really close so they don't charge me interest.

My question is, can I charge the tenant for the cost of mold remediation, and how should I go about it?

They are a freight forwarder that charges by the cubic foot.Be aware, shipping large heavy items to Hawaii is crazy expensive!  

I would not suggest you take a loan from your 401k as there are usually penalties and significant charges that can eat away at your profit. 

You don't want to be in charge of building the marketing pieces it takes too much time.

Here are the laws in regards to this stuff.4735.01 [Effective Until 3/20/2019] Real estate broker definitions.As used in this chapter:(A) "Real estate broker" includes any person, partnership, association, limited liability company, limited liability partnership, or corporation, foreign or domestic, who for another, whether pursuant to a power of attorney or otherwise, and who for a fee, commission, or other valuable consideration, or with the intention, or in the expectation, or upon the promise of receiving or collecting a fee, commission, or other valuable consideration does any of the following:(1) Sells, exchanges, purchases, rents, or leases, or negotiates the sale, exchange, purchase, rental, or leasing of any real estate;(2) Offers, attempts, or agrees to negotiate the sale, exchange, purchase, rental, or leasing of any real estate;(3) Lists, or offers, attempts, or agrees to list, or auctions, or offers, attempts, or agrees to auction, any real estate;(4) Buys or offers to buy, sells or offers to sell, or otherwise deals in options on real estate;(5) Operates, manages, or rents, or offers or attempts to operate, manage, or rent, other than as custodian, caretaker, or janitor, any building or portions of buildings to the public as tenants;(6) Advertises or holds self out as engaged in the business of selling, exchanging, purchasing, renting, or leasing real estate;(7) Directs or assists in the procuring of prospects or the negotiation of any transaction, other than mortgage financing, which does or is calculated to result in the sale, exchange, leasing, or renting of any real estate;(8) Is engaged in the business of charging an advance fee or contracting for collection of a fee in connection with any contract whereby the broker undertakes primarily to promote the sale, exchange, purchase, rental, or leasing of real estate through its listing in a publication issued primarily for such purpose, or for referral of information concerning such real estate to brokers, or both, except that this division does not apply to a publisher of listings or compilations of sales of real estate by their owners;(9) Collects rental information for purposes of referring prospective tenants to rental units or locations of such units and charges the prospective tenants a fee.

I would then contact the property managers and ask for their charges especially what they charge for short term rental marketing. 

An appraiser is going to charge you. 

Self-directed IRA A Solo 401k has several advantages as compared to a Self-Directed IRA including the following which specifically apply to your situation: Unlike a Self-directed IRA, you can have the account for the Solo 401k at a bank or brokerage that does not charge maintenance fees and where you will have checkbook control.Unlike a Self-directed IRA, if you use leverage (which must be non-recourse financing in either case) to acquire real estate with your Solo 401k the income will not be subject to Unrelated Debt Finance Income taxGeneral Considerations Re Investing Retirement Funds in Real Estate:1.

I don't put signs in the yard as you get a lot of tire kickers calling with no idea on how much rent you will charge.