The No. 1 thing you need to do, is to research your local city's requirements, you already mentioned the HOA.
DO NOT BUY ANYTHING UNTIL YOU CHECK WITH YOUR COMMUNITY ZONING AND BUILDING REQUIREMENTS!
A start:
height requirement Article IV Sec 1-226(a)
https://library.municode.com/tx/ful...deId=PTIICOOR_APXAZO_ARTIVSPUSRE_S1-226ACUSST
setbacks Article III Sec. 3-165(b)(5)
https://library.municode.com/tx/fulshear/codes/code_of_ordinances?nodeId=PTIICOOR_APXAZO_ARTIIIDIRE
The codes adopted in your community:
http://www.fulsheartexas.gov/services/building_services/permits.php
These are what your design needs to conform to.
Note that there are materials and design standards also.
Here is info from the packet about applying for a permit. Since you need to submit wind load calculations, you need a registered Professional Engineer (P.E.) to do that and to seal the plans.
http://www.fulsheartexas.gov/Residential Building Permit Packet.pdf
I think that in your case, getting a premanufactured structure meeting all the standards will be much-less frustrating, even if it costs more than the simple expedient of buying the material and building something yourself. You as homeowner are the responsible party, ultimately, for compliance with the local land development code. Ignore those codes, standards, and ordinances at your own risk; to do-so could end-up with you having penalties, fines, and even liens against your property by the municipality.
From the Permit Packet:
Within the City of Fulshear city limits, any owner or authorized agent who intends to construct, enlarge, alter, repair, move, demolish, or change the occupancy of a building or structure, or to erect, install, enlarge, alter, repair, remove, convert or replace any electrical, gas, mechanical or plumbing system (the installation of which is regulated by the International Building Code), or to cause any such work to be done, shall first make application to the Building Official and obtain the required permit.
Any contractor who has done work without the required building permit will be fined $350.00. The paying of this fee shall not relieve any person from fully complying with the requirements in the execution of the work nor from any other penalties prescribed in the Code.
I suggest speaking to the building and zoning departments, and ask them whose premanufactured storage products have been getting approval for installation. This is all public knowledge. Then go talk to those providers. Make sure that your talks with them include permitting charges, that they are fully-insured (ask for binders, and contact the insurance company for peace of mind) you might discover they want to charge you $200 for a permit runner to make the application to the building dept. That may be just the cost of doing business. You could inquire about being the 'permit runner,' and trying to save the $, but don't be surprised if they say, 'no.'
Lastly,
do not place an order for a premanufactured product before the plans are approved for the structure and installation site plan. This will save you the unfortunate experience of trying to get something approved that does not meet their design, size, or structural standards. The manufacturer should be willing to provide you with the
sealed plans prior to you signing a sales contract, even if you have to pay them something for the plans up-front. Believe me, this will be one of the best investments you can make, to save you the frustration, time, and money involved in trying to permit a non-compliant structure.